#include <bits/stdc++.h>
using namespace std;
template <class T>
inline std::string to_string(const T& t) {
  std::stringstream ss;
  ss << t;
  return ss.str();
}
int a[4], n;
int question;
vector<pair<int, char> > str;
vector<int> quesind;
int ind = 0;
string s;
void replace_l(char bosaw, int r) {
  if (quesind.size()) {
    for (int l1 = 1; l1 <= r; l1++) {
      s[quesind[ind++]] = bosaw;
    }
  }
}
int main() {
  std::ios_base::sync_with_stdio(false);
  ;
  cin >> n >> s;
  if (n % 4 != 0) {
    cout << "===" << endl;
    return 0;
  }
  for (int i = 0; i <= n - 1; i++) {
    if (s[i] == 'A')
      a[0]++;
    else if (s[i] == 'C')
      a[1]++;
    else if (s[i] == 'G')
      a[2]++;
    else if (s[i] == 'T')
      a[3]++;
    else {
      question++;
      quesind.push_back(i);
    }
  }
  for (int i = 0; i <= 3; i++) {
    if (a[i] > n / 4) {
      cout << "===" << endl;
      return 0;
    }
  }
  for (int i = 0; i <= 3; i++) {
    if (i == 0) {
      replace_l('A', (n / 4) - a[i]);
    } else if (i == 1) {
      replace_l('C', (n / 4) - a[i]);
    } else if (i == 2) {
      replace_l('G', (n / 4) - a[i]);
    } else {
      replace_l('T', (n / 4) - a[i]);
    }
  }
  for (int l1 = 0; l1 <= n - 1; l1++) cout << s[l1];
  return 0;
}
