#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MONKE = 0;
void solve() {
  string s;
  int n;
  vector<char> v = {'A', 'G', 'C', 'T'};
  map<char, int> cnt;
  cin >> n >> s;
  if (n % 4 != 0) goto no;
  for (auto x : s) cnt[x]++;
  for (auto e : v) {
    if (cnt[e] > n / 4) goto no;
    for (auto &x : s) {
      if (cnt[e] == n / 4) break;
      if (x == '?') {
        x = e;
        cnt[e]++;
      }
    }
  }
  cout << s << endl;
  return;
no:
  cout << "===";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;
  while (t--) {
    solve();
  }
  return MONKE;
}
