#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  if (n % 4 != 0) {
    cout << "===" << endl;
    return 0;
  }
  int num = n / 4, a = 0, t = 0, c = 0, g = 0;
  for (int i = 0; i < s.length(); i++) {
    if (s[i] == 'A') a++;
    if (s[i] == 'C') c++;
    if (s[i] == 'T') t++;
    if (s[i] == 'G') g++;
  }
  if (g > num || c > num || a > num || t > num) {
    cout << "===" << endl;
    return 0;
  }
  for (int i = 0; i < s.length(); i++) {
    if (s[i] == '?') {
      if (a < num) {
        a++;
        s[i] = 'A';
        continue;
      }
      if (c < num) {
        c++;
        s[i] = 'C';
        continue;
      }
      if (g < num) {
        g++;
        s[i] = 'G';
        continue;
      }
      if (t < num) {
        t++;
        s[i] = 'T';
        continue;
      }
    }
  }
  cout << s << endl;
}
