#include <bits/stdc++.h>
using namespace std;
int n, a, c, g, t;
string s;
int M() { return min(min(a, c), min(g, t)); }
int main() {
  cin >> n;
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == 'A') {
      a++;
    } else if (s[i] == 'C') {
      c++;
    } else if (s[i] == 'G') {
      g++;
    } else if (s[i] == 'T') {
      t++;
    }
  }
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == '?') {
      if (a == M()) {
        s[i] = 'A';
        a++;
      } else if (c == M()) {
        s[i] = 'C';
        c++;
      } else if (g == M()) {
        s[i] = 'G';
        g++;
      } else {
        s[i] = 'T';
        t++;
      }
    }
  }
  if (a == c && c == g && g == t) {
    cout << s << endl;
  } else {
    cout << "===" << endl;
  }
  return 0;
}
