1 #define mm(a) memset(a,0,sizeof(a)); 2 #define max(x,y) (x)>(y)?(x):(y) 3 #define min(x,y) (x)<(y)?(x):(y) 4 #define Fopen freopen("1.in","r",stdin); freopen("m.out","w",stdout); 5 #define rep(i,a,b) for(int i=(a);i<=(b);i++) 6 #define per(i,b,a) for(int i=(b);i>=(a);i--) 7 #include<bits/stdc++.h> 8 typedef long long ll; 9 #define PII pair<ll,ll> 10 using namespace std; 11 const int INF=0x3f3f3f3f; 12 const int MAXN=(int)2e5 + 5; 13 const ll mod=1e9+7; 14 15 16 string input,temp; 17 vector<int>v; 18 map<int,int>mp; 19 int n,dp[MAXN],m; 20 int main() { 21 cin>>input; 22 istringstream iss(input); 23 mp.clear(); 24 v.clear(); 25 v.push_back(0); 26 while (getline(iss, temp, ',')) { 27 int x=atoi(temp.c_str()); 28 v.push_back(x); 29 mp[x]++; 30 } 31 n=v.size()-1; 32 int ans; 33 for(auto i:mp) { 34 if(i.second==1)ans=i.first; 35 } 36 printf("%d ",ans); 37 return 0; 38 }