func_code_string: #include <bits/stdc++.h>   using namespace std;   char str[50][30];   char p[30];   char t[30];   int n;   int solve() {     for (int i = 0; i < n; i++) {       if (strstr(str[i], t) != NULL) {         return 0;       }     }     return 1;   }   int main() {     scanf( %d , &n);     for (int i = 0; i < n; i++) {       scanf( %s , &str[i]);     }     p[0] =  a  - 1;     p[1] = 0;     int len = 1;     for (int i = 1;; i++) {       p[0]++;       int j = 0;       while (p[j] ==  z  + 1) {         p[j] =  a ;         j++;         if (p[j] == 0) {           p[j] =  a ;           p[j + 1] = 0;           len = j + 1;         } else {           p[j]++;         }       }       for (int k = 0; k < len; k++) {         t[k] = p[len - k - 1];       }       t[len] = 0;       if (solve() == 1) {         break;       }     }     printf( %s n , t);     return 0;   }   