func_code_string: #include <bits/stdc++.h>   using namespace std;   bool odd(int N) {     while (N < 0) {       N += 2;     }     return N % 2 == 1 ? true : false;   }   bool even(int N) {     while (N < 0) {       N += 2;     }     return N % 2 == 0 ? true : false;   }   int main() {     string s, t;     cin >> s >> t;     int N = s.size();     string result =   ;     int num = 0;     for (int i = 0; i != N; ++i) {       if (s[i] != t[i]) {         ++num;         if (num % 2) {           result += s[i];         } else {           result += t[i];         }       } else {         result += s[i];       }     }     if (even(num)) {       cout << result;     } else {       cout <<  impossible ;     }     return 0;   }   