func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string s, t;     cin >> s >> t;     string p(s.size(),  0 );     int dif = 0;     for (int i = 0; i < s.size(); i++) {       if (s[i] != t[i]) dif++;     }     if (dif % 2 != 0) return cout <<  impossible , 0;     int a(0), b(0);     for (int i = 0; i < s.size(); i++) {       if (s[i] != t[i]) {         if (a <= b) {           p[i] = t[i];           a++;         } else {           p[i] = s[i];           b++;         }       }     }     cout << p;   }   