#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  cin >> n;
  cin >> s;
  if (n % 4 != 0)
    cout << "===" << endl;
  else {
    int k = n / 4;
    int a = 0, c = 0, g = 0, t = 0, q = 0;
    for (char C : s) {
      if (C == 'A')
        a++;
      else if (C == 'C')
        c++;
      else if (C == 'G')
        g++;
      else if (C == 'T')
        t++;
      else
        q++;
    }
    a = k - a;
    c = k - c;
    g = k - g;
    t = k - t;
    if (a < 0 || c < 0 || g < 0 || t < 0) {
      cout << "===" << endl;
      exit(0);
    }
    for (int i = 0; i < s.size(); i++) {
      if (s[i] == '?') {
        if (a > 0) {
          s[i] = 'A';
          a--;
        } else if (c > 0) {
          s[i] = 'C';
          c--;
        } else if (g > 0) {
          s[i] = 'G';
          g--;
        } else if (t > 0) {
          s[i] = 'T';
          t--;
        }
      }
    }
    cout << s << endl;
  }
  return 0;
}
