func_code_string: #include <bits/stdc++.h>   using namespace std;   int a[27] = {0};   int main() {     int i, j, m, n, t;     string s;     cin >> n;     cin >> s;     for (i = 0; i < n; i++) a[s[i] -  a  + 1]++;     for (i = 1; i <= 26; i++)       if (a[i] == n) {         cout <<  NO  << endl;         return 0;       }     for (i = 0; i < n - 1; i++) {       if (s[i] != s[i + 1]) {         cout <<  YES  << endl;         cout << s[i] << s[i + 1] << endl;         return 0;       }     }     return 0;   }   