func_code_string: #include <bits/stdc++.h>   using namespace std;   void populate(string& s, char c, int n) {     for (int i = 0; i < n; ++i) s[s.find_first_of( ? )] = c;   }   int main() {     ios::sync_with_stdio(0);     int n;     cin >> n;     string s;     cin >> s;     auto na = count(s.begin(), s.end(),  A );     auto nc = count(s.begin(), s.end(),  C );     auto ng = count(s.begin(), s.end(),  G );     auto nt = count(s.begin(), s.end(),  T );     auto nq = count(s.begin(), s.end(),  ? );     auto m = max(na, max(nc, (max(ng, nt))));     auto da = m - na;     auto dc = m - nc;     auto dg = m - ng;     auto dt = m - nt;     if (nq < da + dc + dg + dt) {       cout <<  ===  << endl;     } else if ((nq - (da + dc + dg + dt)) % 4 != 0) {       cout <<  ===  << endl;     } else {       populate(s,  A , da);       populate(s,  C , dc);       populate(s,  G , dg);       populate(s,  T , dt);       for (int i = 0; i < (nq - (da + dc + dg + dt)); i += 4) {         populate(s,  A , 1);         populate(s,  C , 1);         populate(s,  G , 1);         populate(s,  T , 1);       }       cout << s << endl;     }   }   