func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0), cout.tie(0);     long long ss4 = 0, ss7 = 0, swap = 0;     string s, t;     cin >> s >> t;     for (long long i = 0; i < s.length(); i++) {       if (s[i] != t[i] && s[i] ==  4 ) {         if (ss7)           ss7--, swap++;         else           ss4++;       } else if (s[i] != t[i] && s[i] ==  7 )         if (ss4)           ss4--, swap++;         else           ss7++;     }     cout << swap + ss7 + ss4 << endl;   }   