func_code_string: #include <bits/stdc++.h>   using namespace std;   map<string, int> m;   string s, c, a;   int n, i, p;   int main() {     for (cin >> n >> s; i < n - 1; i++) {       c += s[i];       c += s[i + 1];       m[c]++;       if (p < m[c]) p = m[c], a = c;       c.clear();     }     cout << a;   }   