func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m;     cin >> n >> m;     char arr1[n][m];     char arr2[m][n];     for (int i = 0; i < n; i++) {       for (int j = 0; j < m; j++) {         char a;         cin >> a;         arr1[i][j] = a;         arr2[j][i] = a;       }     }     string ans =   ;     for (int i = 0; i < n; i++) {       for (int j = 0; j < m; j++) {         if (count(arr1[i], arr1[i] + m, arr1[i][j]) == 1 &&             count(arr2[j], arr2[j] + n, arr1[i][j]) == 1) {           ans += string(1, arr1[i][j]);         }       }     }     cout << ans;   }   