#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string str;
  cin >> str;
  if (n % 4)
    cout << "===" << endl;
  else {
    int na, ng, nt, nc;
    na = ng = nt = nc = n / 4;
    int fl = 1;
    int a = 0, g = 0, t = 0, c = 0, w = 0;
    for (int i = 0; i < n; i++) {
      if (str[i] == 'A') a++;
      if (str[i] == 'G') g++;
      if (str[i] == 'C') c++;
      if (str[i] == 'T') t++;
    }
    if (a > na) fl = 0;
    if (g > ng) fl = 0;
    if (c > nc) fl = 0;
    if (t > nt) fl = 0;
    na -= a;
    ng -= g;
    nt -= t;
    nc -= c;
    if (!fl) {
      cout << "===" << endl;
    } else {
      for (int i = 0; i < str.length(); i++) {
        if (str[i] == '?') {
          if (na) {
            str[i] = 'A';
            na--;
          } else if (nc) {
            str[i] = 'C';
            nc--;
          } else if (ng) {
            str[i] = 'G';
            ng--;
          } else if (nt) {
            str[i] = 'T';
            nt--;
          }
        }
      }
      cout << str << endl;
    }
  }
}
