#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  long long int n;
  string s, a = "ACTG";
  cin >> n >> s;
  map<char, long long int> m;
  if (n % 4) return cout << "===", 0;
  for (long long int i = 0; i < n; i++) {
    if (s[i] != '?') {
      m[s[i]]++;
      if (m[s[i]] > n / 4) return cout << "===", 0;
    }
  }
  for (char c : a) {
    m[c] = n / 4 - m[c];
  }
  for (long long int i = 0; i < n; i++) {
    if (s[i] == '?') {
      for (char c : a) {
        if (m[c] > 0) {
          s[i] = c;
          m[c]--;
          break;
        }
      }
      if (s[i] == '?') return cout << "===", 0;
    }
  }
  cout << s;
}
