func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string a, b, c;     bool yes = true;     int length, i;     cin >> a >> b;     length = a.length();     for (i = 0; i < length; i++) {       if (a[i] < b[i]) {         yes = false;         break;       }     }     if (yes == false) {       cout << -1 << endl;     } else {       cout << b << endl;     }     return 0;   }   