func_code_string: #include <bits/stdc++.h>   using namespace std;   double pi = 3.14159265359;   using namespace std;   int main() {     ios::sync_with_stdio(false);     string a, b;     cin >> a >> b;     string c(a.size(),  0 );     int count = 0;     for (unsigned int i = 0; i < a.size(); i++)       if (a[i] == b[i]) c[i] = a[i], count++;     if ((a.size() - count) % 2)       cout <<  impossible ;     else {       bool ok = 0;       for (unsigned int i = 0; i < a.size(); i++)         if (a[i] != b[i] && !ok)           c[i] = a[i], ok = 1;         else if ((a[i] != b[i] && ok))           c[i] = b[i], ok = 0;       cout << c <<   n ;     }     return 0;   }   