func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string s1, s2;     cin >> s1 >> s2;     int n = s1.length(), k = 0, s;     for (int i = 0; i < n; i++)       if (s1[i] != s2[i]) k++;     if (k % 2 == 1)       printf( impossible );     else {       int s = k / 2;       string ans;       for (int i = 0; i < n; i++)         if (s1[i] != s2[i])           if (s > 0) {             ans += s1[i];             s--;           } else             ans += s2[i];         else           ans += s1[i];       cout << ans;     }     return 0;   }   