func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(false);     ;     string s;     int flag = 0;     cin >> s;     string at =  at , dot =  dot ;     for (int i = 1; i < s.size() - 3; i++) {       if (s.substr(i, 2) == at && flag == 0) {         s.replace(i, 2,  @ );         flag = 1;       }       if (s.substr(i, 3) == dot) {         s.replace(i, 3,  . );       }     }     int j = s.size() - 3;     if (s.substr(j, 2) == at && flag == 0) s.replace(j, 2,  @ );     cout << s;     return 0;   }   