#include <bits/stdc++.h>
using namespace std;
int n, m, k, l, r, ans, a[1111], b[1111];
char ch[4] = {'A', 'C', 'G', 'T'};
int main() {
  string s;
  cin >> n >> s;
  for (int i = 0; i < s.size(); ++i) {
    a[s[i]]++;
  }
  for (int i = 0; i < s.size(); ++i) {
    r = 1e9;
    l = -1;
    for (int j = 0; j < 4; ++j) {
      if (a[ch[j]] < r) {
        r = a[ch[j]];
        l = j;
      }
    }
    if (s[i] == '?') {
      s[i] = ch[l];
      a[ch[l]]++;
    }
  }
  for (int i = 1; i < 4; ++i) {
    if (a[ch[i]] != a[ch[i - 1]]) return cout << "===", 0;
  }
  cout << s;
}
