#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, d = 0, a = 0, c = 0, g = 0, t = 0;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'A')
      a++;
    else if (s[i] == 'C')
      c++;
    else if (s[i] == 'G')
      g++;
    else if (s[i] == 'T')
      t++;
    else if (s[i] == '?')
      d++;
  }
  int p = n / 4;
  if (n % 4 || a > p || c > p || g > p || t > p) {
    cout << "===" << endl;
    return 0;
  } else {
    int a2 = p - a;
    int c2 = p - c;
    int g2 = p - g;
    int t2 = p - t;
    if ((a2 + c2 + g2 + t2) == d) {
      for (int i = 0; i < n; i++) {
        if (s[i] == '?') {
          if (a2 > 0) {
            s[i] = 'A';
            a2--;
            continue;
          }
          if (c2 > 0) {
            s[i] = 'C';
            c2--;
            continue;
          }
          if (g2 > 0) {
            s[i] = 'G';
            g2--;
            continue;
          }
          if (t2 > 0) {
            s[i] = 'T';
            t2--;
            continue;
          }
        }
      }
    }
    cout << s << endl;
  }
  return 0;
}
