Beijing Institute of Technology 2019.6 Monthly Contest (For grade 2018)

北理的18级比我校17级还猛，这上哪儿说理去

A.发现存在长度相等的棒子答案最小值就是0，直接特判

时间复杂度从n ^ 2优化到40 * 40

（一开始没想到 写着分段二分WA7发）

#include <map>
#include <set>
#include <ctime>
#include <cmath>
#include <queue>
#include <stack>
#include <vector>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
#define For(i, x, y) for(int i=x;i<=y;i++)  
#define _For(i, x, y) for(int i=x;i>=y;i--)
#define Mem(f, x) memset(f,x,sizeof(f))  
#define Sca(x) scanf("%d", &x)
#define Sca2(x,y) scanf("%d%d",&x,&y)
#define Sca3(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define Scl(x) scanf("%lld",&x);  
#define Pri(x) printf("%d
", x)
#define Prl(x) printf("%lld
",x);  
#define CLR(u) for(int i=0;i<=N;i++)u[i].clear();
#define LL long long
#define ULL unsigned long long  
#define mp make_pair
#define PII pair<int,int>
#define PIL pair<int,long long>
#define PLL pair<long long,long long>
#define pb push_back
#define fi first
#define se second 
typedef vector<int> VI;
int read(){int x = 0,f = 1;char c = getchar();while (c<'0' || c>'9'){if (c == '-') f = -1;c = getchar();}
while (c >= '0'&&c <= '9'){x = x * 10 + c - '0';c = getchar();}return x*f;}
const double eps = 1e-6;
const int maxn = 1e5 + 10;
const int INF = 0x3f3f3f3f;
const int mod = 1e9 + 7; 
int N,M,K;
struct node{
    int fi,se,id;
};
node a[maxn];
bool cmp(node a,node b){
    return a.id < b.id;
}
int MAX[50],MIN[50];
struct fen{
    LL son,mon;
    fen(){}
    fen(LL son,LL mon):son(son),mon(mon){}
    friend bool operator < (fen a,fen b){
        return a.son * b.mon < b.son * a.mon;
    }
    friend bool operator == (fen a,fen b){
        return (a.son * b.mon) == (b.son * a.mon);
    }
};
vector<int>Q[50]; 
int main(){
    Sca(N); 
    for(int i = 1; i <= N ; i ++){
        a[i].fi = read(); a[i].se = read();
        Q[a[i].fi].push_back(i);
        a[i].id = i;
    } 
    int u = INF,v = INF;
    bool flag = 0;
    for(int i = 1; i <= 40; i ++){
        if(Q[i].size() > 1){
            flag = 1;
            int uu = Q[i][0],vv = Q[i][1];
            if(uu < u || (uu == u && vv < v)){
                u = uu; v = vv;
            }
        }
    }
    if(flag){
        printf("%d %d",u,v);
        return 0;
    }

    fen ans = fen(INF,1);
    sort(a + 1,a + 1 + N,cmp);
    for(int i = 1; i <= N ; i ++){
        for(int j = i + 1; j <= N ; j ++){
            fen x = fen(max(a[i].se,a[j].se) * abs(a[j].fi - a[i].fi),min(a[i].se,a[j].se));
            if(x < ans){
                ans = x;
                u = a[i].id,v = a[j].id;
            }
        }
    }
    printf("%d %d
",u,v);
    return 0;
}

B.没啥好说的，找了规律暴力模拟，只要有耐心就能写出来的题

#include <map>
#include <set>
#include <ctime>
#include <cmath>
#include <queue>
#include <stack>
#include <vector>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
#define For(i, x, y) for(int i=x;i<=y;i++)  
#define _For(i, x, y) for(int i=x;i>=y;i--)
#define Mem(f, x) memset(f,x,sizeof(f))  
#define Sca(x) scanf("%d", &x)
#define Sca2(x,y) scanf("%d%d",&x,&y)
#define Sca3(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define Scl(x) scanf("%lld",&x);  
#define Pri(x) printf("%d
", x)
#define Prl(x) printf("%lld
",x);  
#define CLR(u) for(int i=0;i<=N;i++)u[i].clear();
#define LL long long
#define ULL unsigned long long  
#define mp make_pair
#define PII pair<int,int>
#define PIL pair<int,long long>
#define PLL pair<long long,long long>
#define pb push_back
#define fi first
#define se second 
typedef vector<int> VI;
int read(){int x = 0,f = 1;char c = getchar();while (c<'0' || c>'9'){if (c == '-') f = -1;c = getchar();}
while (c >= '0'&&c <= '9'){x = x * 10 + c - '0';c = getchar();}return x*f;}
const double eps = 1e-9;
const int maxn = 510;
const int INF = 0x3f3f3f3f;
const int mod = 1e9 + 7; 
int a,b,c;
char MAP[maxn][maxn];
int main(){
    int T; Sca(T);
    while(T--){
        Sca3(a,b,c);
        int w = 2 * a + 1 + 2 * b;
        int h = 2 * c + 1 + 2 * b;
        for(int i = 1; i <= h; i ++ ){
            for(int j = 1; j <= w; j ++) MAP[i][j] = '?';
        }
        for(int i = 1; i <= h; i ++){
            for(int j = 1; j <= w ; j ++){
                if(h - i + j <= 2 * b) MAP[i][j] = '.';
                if(i + w - j <= 2 * b) MAP[i][j] = '.';
             }
        }
        int l = min(h / 4,b);
        /*for(int i = 3; i <= h;i += 2){
            int x = min(i,h - i + 1);
            x /= 2;
            x = min(x,b);
            if(i < h - i + 1){
                for(int j = 1; j <= x; j++){
                    MAP[i][j * 2] = 'p';
                }
            }else{
                for(int j = l; j >= l - x + 1; j --){
                    MAP[i][j * 2] = 'p';
                }
            }
        } */
        for(int i = 2; i <= 2 * b; i += 2){
            for(int j = i + 1; j <= w; j += 2) MAP[i][j] = '.';
        }
        for(int i = 2 * b + 2; i <= h; i += 2){
            for(int j = 2 * b + 2; j <= w; j += 2) MAP[i][j] = '.';
        }
        for(int i = 1; i <= h; i += 2){
            for(int j = 1; j <= w; j ++){
                if(MAP[i][j] == '.' || MAP[i][j] == 'p') continue;
                int cnt = 0;
                if(2 * b >= i - 1){
                    cnt = 2 * b - i + 1;
                }
                if(j & 1) MAP[i][j] = '+';
                else if(w - j + 1 - cnt <= 2 * a){
                    MAP[i][j] = '-';
                } 
                else MAP[i][j] = '.';
            }
        }
        for(int i = 2; i <= h ; i += 2){
            for(int j = 1; j <= w; j ++){
                if(MAP[i][j] == '.') continue;
                if(j & 1) MAP[i][j] = '|';
                else MAP[i][j] = '\';
            }
        }
        for(int i = 1; i <= h; i ++){
            for(int j = 1; j <= w; j ++){
                cout << MAP[i][j];
            }
            if(i == h && !T) continue;
            else cout << endl; 
        }
    }
    return 0;
}

C.暴力判11个位置插入的符号，(不插入,+,-,*)四种情况，然后表达式求值判断，时间复杂度4 ^ 11 * 24

常数很大，我又菜，表达式求值写的跟*一样自己都看不下去了，手写了个栈才卡过去

#include <map>
#include <set>
#include <ctime>
#include <cmath>
#include <queue>
#include <stack>
#include <vector>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
#define For(i, x, y) for(int i=x;i<=y;i++)  
#define _For(i, x, y) for(int i=x;i>=y;i--)
#define Mem(f, x) memset(f,x,sizeof(f))  
#define Sca(x) scanf("%d", &x)
#define Sca2(x,y) scanf("%d%d",&x,&y)
#define Sca3(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define Scl(x) scanf("%lld",&x);  
#define Pri(x) printf("%d
", x)
#define Prl(x) printf("%lld
",x);  
#define CLR(u) for(int i=0;i<=N;i++)u[i].clear();
#define LL long long
#define ULL unsigned long long  
#define mp make_pair
#define PII pair<int,int>
#define PIL pair<int,long long>
#define PLL pair<long long,long long>
#define pb push_back
#define fi first
#define se second 
typedef vector<int> VI;
int read(){int x = 0,f = 1;char c = getchar();while (c<'0' || c>'9'){if (c == '-') f = -1;c = getchar();}
while (c >= '0'&&c <= '9'){x = x * 10 + c - '0';c = getchar();}return x*f;}
const double eps = 1e-9;
const int maxn = 110;
const int INF = 0x3f3f3f3f;
const int mod = 1e9 + 7; 
int N,M,K;
LL y;
char Stack[maxn];
int cnt,tot;
int ans = 0;
char str[20];
PIL S[maxn];
bool check(){
    int top = 0;
    LL num = 0; bool flag = 0;
    for(int i = 1; i <= tot; i ++){
        if(Stack[i] >= '0' && Stack[i] <= '9'){
            if(!num && flag) return 0;
            num = num * 10 + Stack[i] - '0';
            flag = 1;
        }else if(Stack[i] == '-'){
            if(flag){
                while(top && S[top].fi == 2 && S[top].se == 3){
                    top--;
                    num *= S[top].se;
                    top--;
                }
                S[++top] = mp(1,num);
                num = 0;
            } 
            S[++top] = mp(2,1);
            flag = 0;
        }else if(Stack[i] == '+'){
            if(flag){
                while(top && S[top].fi == 2 && S[top].se == 3){
                    top--;
                    num *= S[top].se;
                    top--;
                }
                S[++top] = mp(1,num);
                num = 0;
            } 
            S[++top] = mp(2,2);
            flag = 0;
        }else if(Stack[i] == '*'){
            if(flag){
                while(top && S[top].fi == 2 && S[top].se == 3){
                    top--;
                    num *= S[top].se;
                    top--;
                }
                S[++top] = mp(1,num);
                num = 0;
            } 
            S[++top] = mp(2,3);
            flag = 0;
        }
    }
    if(flag){
        while(top && S[top].fi == 2 && S[top].se == 3){
            top--;
            num *= S[top].se;
            top--;
        }
        S[++top] = mp(1,num);
        num = 0;
    } 
    LL ans = 0;
    while(top){
        PIL u = S[top]; top--;
        if(!top){
            ans += u.se;
            break;
        } 
        if(S[top].se == 1) ans -= u.se;
        else ans += u.se;
        top--;
    }
//    if(ans == y){
//        for(int i = 1; i <= tot; i ++){
//            printf("%c",Stack[i]);
//        }
//        puts("");
//    }
    return ans == y;
}

void dfs(int pos){
    Stack[++tot] = str[pos];
    if(pos == cnt){
        if(check()) ans++;
        tot--;
        return;
    }
    Stack[++tot] = '-';
    dfs(pos + 1);
    tot--;
    Stack[++tot] = '+';
    dfs(pos + 1);
    tot--;
    Stack[++tot] = '*';
    dfs(pos + 1);
    tot--;
    dfs(pos + 1);
    tot--;
}

int main(){
    scanf("%s",str); Scl(y);
    tot = 0;
    cnt = strlen(str) - 1;
    dfs(0);
    Pri(ans);
    return 0;
}

D.搞个优先队列按照还剩下字母多少排序，每次输出剩下字母最多的那个字母

如果有一种字母的数量超过了一半左右就NO

#include <map>
#include <set>
#include <ctime>
#include <cmath>
#include <queue>
#include <stack>
#include <vector>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
#define For(i, x, y) for(int i=x;i<=y;i++)  
#define _For(i, x, y) for(int i=x;i>=y;i--)
#define Mem(f, x) memset(f,x,sizeof(f))  
#define Sca(x) scanf("%d", &x)
#define Sca2(x,y) scanf("%d%d",&x,&y)
#define Sca3(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define Scl(x) scanf("%lld",&x);  
#define Pri(x) printf("%d
", x)
#define Prl(x) printf("%lld
",x);  
#define CLR(u) for(int i=0;i<=N;i++)u[i].clear();
#define LL long long
#define ULL unsigned long long  
#define mp make_pair
#define PII pair<int,int>
#define PIL pair<int,long long>
#define PLL pair<long long,long long>
#define pb push_back
#define fi first
#define se second 
typedef vector<int> VI;
int read(){int x = 0,f = 1;char c = getchar();while (c<'0' || c>'9'){if (c == '-') f = -1;c = getchar();}
while (c >= '0'&&c <= '9'){x = x * 10 + c - '0';c = getchar();}return x*f;}
const double eps = 1e-9;
const int maxn = 1e5 + 10;
const int INF = 0x3f3f3f3f;
const int mod = 1e9 + 7; 
int N,M,K;
char str[maxn];
int num[30];
struct node{
    int id,n;
    node(){}
    node(int id,int n):id(id),n(n){}
    friend bool operator < (node a,node b){
        return a.n < b.n;
    }
};
int main(){
    scanf("%s",str);
    int MAX = 0,l = strlen(str);
    for(int i = 0;str[i]; i ++) num[str[i] - 'a']++;
    for(int i = 0 ; i < 26; i ++) MAX = max(MAX,num[i]);
    if((l & 1) && (MAX > l / 2 + 1)){
        puts("NO"); return 0;
    }
    if(!(l & 1) && (MAX > l / 2)){
        puts("NO"); return 0;
    }
    priority_queue<node>Q;
    for(int i = 0 ; i < 26; i ++){
        if(num[i]) Q.push(node(i,num[i]));
    }
    int la = 100;
    while(!Q.empty()){
        node u = Q.top(),v; Q.pop();
        if(la == u.id){
            v = Q.top(); Q.pop();
            Q.push(u); u = v;
        }
        printf("%c",u.id + 'a');
        u.n--; la = u.id;
        if(u.n > 0) Q.push(u);
    }
    return 0;
}

E.求和公式都会8，(a[1] + a[1] + n - 1) * n = 2 * N

枚举一下n，判断a[1]是否符合条件，时间复杂度根号N

#include <map>
#include <set>
#include <ctime>
#include <cmath>
#include <queue>
#include <stack>
#include <vector>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
#define For(i, x, y) for(int i=x;i<=y;i++)  
#define _For(i, x, y) for(int i=x;i>=y;i--)
#define Mem(f, x) memset(f,x,sizeof(f))  
#define Sca(x) scanf("%d", &x)
#define Sca2(x,y) scanf("%d%d",&x,&y)
#define Sca3(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define Scl(x) scanf("%lld",&x);  
#define Pri(x) printf("%d
", x)
#define Prl(x) printf("%lld
",x);  
#define CLR(u) for(int i=0;i<=N;i++)u[i].clear();
#define LL long long
#define ULL unsigned long long  
#define mp make_pair
#define PII pair<int,int>
#define PIL pair<int,long long>
#define PLL pair<long long,long long>
#define pb push_back
#define fi first
#define se second 
typedef vector<int> VI;
int read(){int x = 0,f = 1;char c = getchar();while (c<'0' || c>'9'){if (c == '-') f = -1;c = getchar();}
while (c >= '0'&&c <= '9'){x = x * 10 + c - '0';c = getchar();}return x*f;}
const double eps = 1e-9;
const int maxn = 110;
const int INF = 0x3f3f3f3f;
const int mod = 1e9 + 7; 
LL N,X;
int check(LL i){
    if((N / i - i + 1) & 1) return 0;
    LL a = (N / i - i + 1) / 2;
    return a > 0;
}
int main(){
    int T; Sca(T);
    while(T--){
        Scl(X); //ll
        N = X * 2;
        int ans = 0;
        for(LL i = 1; i * i <= N; i ++){
            if(N % i) continue;
            ans += check(i);
            if(i * i != N) ans += check(N / i);
        }
        Pri(ans);
    }
    return 0;
}

F.提供一手敲了一个多小时的CE代码

个人觉得本题的正解是离散化之后上线段树区间求和区间修改，问题在于mod 2 ^ 64的这个操作ULL都存不下，大数模板里也没有对大数取模这个操作

我个人觉得__int128可以过，但是gym这个oj的所有提交语言都CE了__int128,这让敲了一个小时的我上哪里说理去。

或许出题人把mod设置为2 ^ 64的意思是让我开64颗线段树按位处理？

后记：晚上睡觉的时候突然开始想出题人为什么要出(1 << 64)这么一个奇怪的取模数

他肯定不是为了开大数，一定有他自己的一套想法，说起来这个数似乎挺特殊的

这不是unsigned long long 自动取模的那个数吗？

操

现在的代码可以AC了

#include <map>
#include <set>
#include <ctime>
#include <cmath>
#include <queue>
#include <stack>
#include <vector>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
#define For(i, x, y) for(int i=x;i<=y;i++)  
#define _For(i, x, y) for(int i=x;i>=y;i--)
#define Mem(f, x) memset(f,x,sizeof(f))  
#define Sca(x) scanf("%d", &x)
#define Sca2(x,y) scanf("%d%d",&x,&y)
#define Sca3(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define Scl(x) scanf("%lld",&x);  
#define Pri(x) printf("%d
", x)
#define Prl(x) printf("%lld
",x);  
#define CLR(u) for(int i=0;i<=N;i++)u[i].clear();
#define LL long long
#define ULL unsigned long long  
#define mp make_pair
#define PII pair<int,int>
#define PIL pair<int,long long>
#define PLL pair<long long,long long>
#define pb push_back
#define fi first
#define se second 
typedef vector<int> VI;
LL read(){LL x = 0,f = 1;char c = getchar();while (c<'0' || c>'9'){if (c == '-') f = -1;c = getchar();}
while (c >= '0'&&c <= '9'){x = x * 10 + c - '0';c = getchar();}return x*f;}
const double eps = 1e-9;
const int maxn = 8e5 + 10;
LL N;
int M;
struct Query{
    int op;
    LL a,b,c;
}query[maxn];
LL Hash[maxn * 2];
struct Tree{
    int l,r;
    ULL sum,lazy;
}tree[maxn * 4];
void Build(int t,int l,int r){
    tree[t].l = l; tree[t].r = r;
    tree[t].sum = tree[t].lazy = 0;
    if(r - l <= 1) return;
    int m = l + r >> 1;
    Build(t << 1,l,m);
    Build(t << 1 | 1,m,r);
}
void Pushup(int t){
    tree[t].sum = tree[t << 1].sum + tree[t << 1 | 1].sum;
}
void solve(int t,ULL p){
    tree[t].lazy = p + tree[t].lazy;
    tree[t].sum = tree[t].sum + ((ULL)Hash[tree[t].r] - (ULL)Hash[tree[t].l]) * p;
}
void Pushdown(int t){
    if(tree[t].lazy){
        solve(t << 1,tree[t].lazy);
        solve(t << 1 | 1,tree[t].lazy);
        tree[t].lazy = 0;
    }
}
void update(int t,int l,int r,ULL p){
    if(l <= tree[t].l && tree[t].r <= r){
        solve(t,p);
        return;        
    }    
    Pushdown(t);
    int m = (tree[t].l + tree[t].r) >> 1;
    if(r <= m) update(t << 1,l,r,p);
    else if(l >= m) update(t << 1 | 1,l,r,p);
    else{
        update(t << 1,l,m,p);
        update(t << 1 | 1,m,r,p);
    }
    Pushup(t);
}
ULL _query(int t,int l,int r){
    if(l <= tree[t].l && tree[t].r <= r){
        return tree[t].sum;
    }
    Pushdown(t);
    int m = (tree[t].l + tree[t].r) >> 1;
    if(r <= m) return _query(t << 1,l,r);
    else if(l >= m) return _query(t << 1 | 1,l,r);
    else{
        return _query(t << 1,l,m) + _query(t << 1 | 1,m,r);
    }
}
int main(){
    cin >> N >> M;
    int cnt = 0;
    for(int i = 1; i <= M; i ++){
        query[i].op = read();
        query[i].a = read();
        query[i].b = read();
        if(query[i].op == 1) query[i].c = read();
        Hash[++cnt] = query[i].a;
       // Hash[++cnt] = query[i].b;
        Hash[++cnt] = query[i].b + 1;
    }    
    sort(Hash + 1,Hash + 1 + cnt);
    cnt = unique(Hash + 1,Hash + 1 + cnt) - Hash - 1;
    Build(1,1,cnt);
    for(int i = 1; i <= M; i ++){
        query[i].a = lower_bound(Hash + 1,Hash + 1 + cnt,query[i].a) - Hash;
        query[i].b = lower_bound(Hash + 1,Hash + 1 + cnt,query[i].b + 1) - Hash;
        if(query[i].op == 1) update(1,query[i].a,query[i].b,query[i].c);
        else{
            ULL ans = _query(1,query[i].a,query[i].b);
            cout << ans << endl;
        }
    }
    return 0;
}

K.喜闻乐见数位dp

太久没敲了水平菜的要死，敲出来的数位dp我自己都看不下去了

#include <map>
#include <set>
#include <ctime>
#include <cmath>
#include <queue>
#include <stack>
#include <vector>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
#define For(i, x, y) for(int i=x;i<=y;i++)  
#define _For(i, x, y) for(int i=x;i>=y;i--)
#define Mem(f, x) memset(f,x,sizeof(f))  
#define Sca(x) scanf("%d", &x)
#define Sca2(x,y) scanf("%d%d",&x,&y)
#define Sca3(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define Scl(x) scanf("%lld",&x);  
#define Pri(x) printf("%d
", x)
#define Prl(x) printf("%lld
",x);  
#define CLR(u) for(int i=0;i<=N;i++)u[i].clear();
#define LL long long
#define ULL unsigned long long  
#define mp make_pair
#define PII pair<int,int>
#define PIL pair<int,long long>
#define PLL pair<long long,long long>
#define pb push_back
#define fi first
#define se second 
typedef vector<int> VI;
int read(){int x = 0,f = 1;char c = getchar();while (c<'0' || c>'9'){if (c == '-') f = -1;c = getchar();}
while (c >= '0'&&c <= '9'){x = x * 10 + c - '0';c = getchar();}return x*f;}
const double eps = 1e-9;
const int maxn = 20;
const int INF = 0x3f3f3f3f;
const int mod = 1e9 + 7; 
int N,M,K;
int str[maxn];
LL dp[maxn][12];
LL ten[maxn],c[maxn];
LL dfs(int pos,LL num,int limit){
    if(pos == 0) return num;
    if(~dp[pos][num] && !limit) return dp[pos][num];
    int top = limit?str[pos - 1]:9;
    LL ans = 0;
    for(int i = 0 ; i <= top; i ++){
        ans += dfs(pos - 1,i,str[pos - 1] == i && limit);
    }
    if(limit) ans += num * (c[pos - 1] + 1);
    else ans += num * ten[pos];
    if(!limit) dp[pos][num] = ans;
    return ans;
}
LL solve(LL x){
    if(!x) return 0;
    Mem(dp,-1);
    int cnt = 0;
    while(x){
        if(!cnt) c[cnt] = x % 10;
        else c[cnt] = ten[cnt] * (x % 10) + c[cnt - 1];
        str[cnt++] = x % 10;
        x /= 10;
    }
    str[cnt] = 0;
    LL ans = dfs(cnt,0,1);
    return ans;
}
int main(){
    ten[0] = 1;
    for(int i = 1; i <= 17; i ++) ten[i] = ten[i - 1] * 10;
    LL l,r; scanf("%lld%lld",&l,&r);
    Prl(solve(r) - solve(l - 1));
    return 0;
}