#include <bits/stdc++.h>
using namespace std;
map<char, int> mp, mp2;
int x, n;
int main() {
  cin >> n;
  string s;
  cin >> s;
  mp['A'] = mp['C'] = mp['G'] = mp['T'] = 0;
  for (int i = 0; i < (int)s.size(); i++) {
    if (s[i] == '?')
      continue;
    else {
      mp[s[i]]++;
    }
  }
  if (mp['A'] > n / 4 || mp['C'] > n / 4 || mp['G'] > n / 4 ||
      mp['T'] > n / 4 || n % 4)
    cout << "===";
  else {
    for (int i = 0; i < (int)s.size(); i++) {
      if (s[i] == '?') {
        if (mp['A'] < n / 4) {
          s[i] = 'A';
          mp['A']++;
        } else if (mp['C'] < n / 4) {
          s[i] = 'C';
          mp['C']++;
        } else if (mp['G'] < n / 4) {
          s[i] = 'G';
          mp['G']++;
        } else if (mp['T'] < n / 4) {
          s[i] = 'T';
          mp['T']++;
        }
      }
    }
    if (mp['A'] != n / 4 || mp['G'] != n / 4 || mp['C'] != n / 4 ||
        mp['T'] != n / 4)
      cout << "===";
    else {
      cout << s;
    }
  }
  return 0;
}
