#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, A = 0, G = 0, C = 0, T = 0, Q = 0;
  cin >> n;
  string s;
  cin >> s;
  for (long long int i = 0; i < n; i++) {
    if (s[i] == 'A') A++;
    if (s[i] == 'G') G++;
    if (s[i] == 'C') C++;
    if (s[i] == 'T') T++;
    if (s[i] == 'Q') Q++;
  }
  if (n % 4 != 0)
    return cout << "===" << endl, 0;
  else {
    if (A <= n / 4 && G <= n / 4 && C <= n / 4 && T <= n / 4) {
      if (Q == 0 && A == n / 4 && G == n / 4 && C == n / 4 && T == n / 4)
        return cout << s << endl, 0;
      for (long long int i = 0; i < n; i++) {
        if (s[i] != '?')
          cout << s[i];
        else {
          if (A < n / 4) {
            cout << 'A';
            A++;
          } else if (G < n / 4) {
            cout << 'G';
            G++;
          } else if (C < n / 4) {
            cout << 'C';
            C++;
          } else {
            cout << 'T';
            T++;
          }
        }
      }
    } else
      return cout << "===" << endl, 0;
  }
  return 0;
}
