#include <bits/stdc++.h>
using namespace std;
void solve_this() {
  long long int i, n, x, y, a = 0, g = 0, c = 0, t = 0, mx, u = 0;
  long long int arr[4];
  cin >> n;
  string str;
  cin >> str;
  for (i = 0; i < n; i++) {
    if (str[i] == 'A')
      a++;
    else if (str[i] == 'G')
      g++;
    else if (str[i] == 'C')
      c++;
    else if (str[i] == 'T')
      t++;
    else
      u++;
  }
  mx = max(max(a, max(g, c)), t);
  x = mx - a + mx - g + mx - c + mx - t;
  if (u >= x && (u - x) % 4 == 0) {
    y = (u - x) / 4;
    arr[0] = mx - a + y;
    arr[1] = mx - g + y;
    arr[2] = mx - c + y;
    arr[3] = mx - t + y;
    for (i = 0; i < n; i++) {
      if (str[i] == '?') {
        if (arr[0] > 0) {
          str[i] = 'A';
          arr[0]--;
        } else if (arr[1] > 0) {
          str[i] = 'G';
          arr[1]--;
        } else if (arr[2] > 0) {
          str[i] = 'C';
          arr[2]--;
        } else if (arr[3] > 0) {
          str[i] = 'T';
          arr[3]--;
        }
      }
    }
    cout << str;
  } else
    cout << "===";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  solve_this();
  return 0;
}
