func_code_string: #include <bits/stdc++.h>   using namespace std;   int a, c, d[205], f, n, b, x, i;   string s, s1, s11, s12;   char i1, i2, j;   int main() {     cin >> n;     for (i = 1; i <= n; i++) {       cin >> s1;       b = s1.size();       c = c + b;       s = s +  % ;       s = s + s1;     }     c = c + n - 1;     for (i1 =  a ; i1 <=  z ; i1++) {       s1 = i1;       x = s.find(s1);       if (x == -1) {         cout << s1;         return 0;       }     }     for (i1 =  a ; i1 <=  z ; i1++) {       for (i2 =  a ; i2 <=  z ; i2++) {         s11 = i1;         s12 = i2;         s1 = s11 + s12;         x = s.find(s1);         if (x == -1) {           cout << s1;           return 0;         }       }     }   }   