#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<char> v;
  vector<char> vv;
  map<char, int> mp;
  map<char, int>::iterator it;
  for (int i = 0; i < n; i++) {
    char c;
    cin >> c;
    v.push_back(c);
    if (c != '?') {
      mp[c]++;
    }
  }
  if (n % 4 != 0) {
    cout << "===";
  } else {
    if (mp['A'] > n / 4 || mp['C'] > n / 4 || mp['G'] > n / 4 ||
        mp['T'] > n / 4) {
      cout << "===";
    } else {
      for (it = mp.begin(); it != mp.end(); it++) {
        for (int i = 0; i < n / 4 - it->second; i++) {
          vv.push_back(it->first);
        }
      }
      int j = 0;
      for (int i = 0; i < v.size(); i++) {
        if (v[i] == '?') {
          v[i] = vv[j];
          j++;
        }
      }
      for (int i = 0; i < v.size(); i++) {
        cout << v[i];
      }
    }
  }
}
