P1516 青蛙的约会

P1516 青蛙的约会
x+mt-p1L=y+nt-p2L
(m-n)t+L(p2-p1)=y-x
令p=p2-p1
(m-n)t+Lp=y-x
然后套扩欧就完事了

#include<iostream>
#include<cstdio>
#include<queue>
#include<algorithm>
#include<cmath>
#include<ctime>
#include<set>
#include<map>
#include<stack>
#include<cstring>
#define inf 2147483647
#define ls rt<<1
#define rs rt<<1|1
#define lson ls,nl,mid,l,r
#define rson rs,mid+1,nr,l,r
#define N 100010
#define For(i,a,b) for(long long i=a;i<=b;i++)
#define p(a) putchar(a)
#define g() getchar()

using namespace std;
long long x,y,m,n,L,g;
long long a,b,c,t,p;
long long flag=1;
void in(long long &x){
    long long y=1;
    char c=g();x=0;
    while(c<'0'||c>'9'){
        if(c=='-')y=-1;
        c=g();
    }
    while(c<='9'&&c>='0'){
        x=(x<<1)+(x<<3)+c-'0';c=g();
    }
    x*=y;
}
void o(long long x){
    if(x<0){
        p('-');
        x=-x;
    }
    if(x>9)o(x/10);
    p(x%10+'0');
}

long long gcd(long long a,long long b){
    return b==0?a:gcd(b,a%b);
}

void exgcd(long long a,long long b,long long &x,long long &y){
    if(!b){
        x=1;
        y=0;
        return;
    }
    exgcd(b,a%b,x,y);
    long long temp=x;
    x=y;
    y=temp-(a/b)*y;
}

int main(){
    in(x);in(y);in(m);in(n);in(L);
    if(m-n<0)
        flag=-1;
    a=max(m-n,n-m);
    b=L;
    g=gcd(a,b);
    if((y-x)%g!=0){
        cout<<"Impossible";
        return 0;
    }
    exgcd(a,b,t,p);
    t*=flag;
    t*=(y-x)/g;
    p*=(y-x)/g;
    b/=g;
    o((t%b+b)%b);
    return 0;
}