func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios::sync_with_stdio(false);     int n, pos;     string s;     cin >> n >> s;     bool flag = false;     for (int i = 1; i < n; i++) {       if (s[i] == s[i - 1])         continue;       else {         flag = true;         pos = i;         break;       }     }     if (flag)       cout <<  YES  << endl, cout << s[pos - 1] << s[pos] << endl;     else       cout <<  NO  << endl;     return 0;   }   