func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string s, t;     cin >> s >> t;     for (long i = s.size() - 1; i >= 0; i--) {       if (s[i] ==  z ) {         s[i] =  a ;       } else {         s[i]++;         break;       }     }     if (s == t) {       cout <<  No such string ;     } else {       cout << s;     }     return 0;   }   