func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T>   T gcd(T a, T b) {     while (a > 0 && b > 0) {       if (a > b)         a %= b;       else         b %= a;     }     return a + b;   }   void YES_NO(bool YES_NO, bool isExit = true) {     if (YES_NO)       cout <<  YES  << endl;     else       cout <<  NO  << endl;     if (isExit) {       exit(0);     }   }   void Yes_No(bool Yes_No, bool isExit = true) {     if (Yes_No)       cout <<  Yes  << endl;     else       cout <<  No  << endl;     if (isExit) {       exit(0);     }   }   void yes_no(bool yes_no, bool isExit = true) {     if (yes_no)       cout <<  yes  << endl;     else       cout <<  no  << endl;     if (isExit) {       exit(0);     }   }   int main() {     string s, t;     cin >> s;     cin >> t;     int cnt = 0;     for (int i = 0; i < s.size(); ++i) {       if (s[i] != t[i]) {         ++cnt;       }     }     if (cnt % 2 == 1) {       cout <<  impossible  << endl;       return 0;     }     cnt /= 2;     string ans = s;     for (int i = 0; i < s.size(); ++i) {       if (s[i] != t[i] && cnt) {         ans[i] = t[i];         --cnt;       }     }     cout << ans << endl;     return 0;   }   