func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(NULL);     cout.tie(NULL);     string s1, s2;     cin >> s1 >> s2;     long long i, n = s1.size(), k1 = 0, k2 = 0, flag = 0, cnt = 0;     for (i = 0; i < n; i++) {       if (s1[i] ==  4  && s2[i] ==  7 )         k1++;       else if (s1[i] ==  7  && s2[i] ==  4 )         k2++;     }     if (k1 >= k2) {       cnt = k2 + (k1 - k2);     } else {       cnt = k1 + (k2 - k1);     }     cout << cnt;     return 0;   }   