#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  map<char, int> m;
  map<char, int>::iterator it1;
  cin >> s;
  if (n % 4 != 0) {
    cout << "===";
    return 0;
  }
  m['A'] = 0;
  m['C'] = 0;
  m['G'] = 0;
  m['T'] = 0;
  map<char, int>::iterator it = m.begin();
  for (int i = 0; i < s.size(); i++) {
    if (s[i] != '?') {
      m[s[i]]++;
    }
  }
  for (it1 = m.begin(); it1 != m.end(); it1++) {
    if (it1->second > (n / 4)) {
      cout << "===";
      return 0;
    }
  }
  int j = 0;
  while (it != m.end() && j < n) {
    if (s[j] != '?') {
      j++;
    }
    if (it->second == n / 4) {
      it++;
    }
    if (s[j] == '?' && it->second < n / 4) {
      s[j] = it->first;
      m[s[j]]++;
    }
  }
  cout << s;
  return 0;
}
