#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC optimize("no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
using namespace std;
using matrix = vector<vector<long long>>;
const int MAXN = 1000;
int cnt[MAXN];
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  string s;
  cin >> n >> s;
  if (n % 4 != 0) {
    cout << "===";
    return 0;
  }
  for (int i = 0; i < n; ++i) {
    if (s[i] != '?') {
      cnt[s[i]]++;
      if (cnt[s[i]] > n / 4) {
        cout << "===";
        return 0;
      }
    }
  }
  for (int i = 0; i < n; ++i) {
    if (s[i] == '?') {
      if (cnt['A'] < n / 4) {
        s[i] = 'A';
        cnt['A']++;
      } else if (cnt['C'] < n / 4) {
        s[i] = 'C';
        cnt['C']++;
      } else if (cnt['G'] < n / 4) {
        s[i] = 'G';
        cnt['G']++;
      } else if (cnt['T'] < n / 4) {
        s[i] = 'T';
        cnt['T']++;
      }
    }
  }
  cout << s;
}
