#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string str;
  cin >> str;
  if (n % 4 != 0) {
    cout << "===" << endl;
    return 0;
  }
  int subWant = n / 4;
  int a[5] = {0};
  for (auto ch : str) {
    if (ch == 'A') {
      ++a[0];
    } else if (ch == 'C') {
      ++a[1];
    } else if (ch == 'T') {
      ++a[2];
    } else if (ch == 'G') {
      ++a[3];
    } else {
      ++a[4];
    }
  }
  if (a[0] > subWant || a[1] > subWant || a[2] > subWant || a[3] > subWant) {
    cout << "===" << endl;
  } else {
    string ans = "";
    int num1 = subWant - a[0];
    int num2 = subWant - a[1];
    int num3 = subWant - a[2];
    int num4 = subWant - a[3];
    for (auto ch : str) {
      if (ch != '?') {
        ans += ch;
      } else {
        if (num1) {
          ans += 'A';
          --num1;
        } else if (num2) {
          ans += 'C';
          --num2;
        } else if (num3) {
          ans += 'T';
          --num3;
        } else if (num4) {
          ans += 'G';
          --num4;
        }
      }
    }
    cout << ans << endl;
  }
  return 0;
}
