#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int a[27] = {0};
  for (int i = 0; i < n; i++) {
    if (s[i] != '?') {
      a[s[i] - 'A']++;
    } else {
      a[26]++;
    }
  }
  vector<int> v;
  v.push_back(a[0]);
  v.push_back(a['T' - 'A']);
  v.push_back(a[2]);
  v.push_back(a['G' - 'A']);
  sort(v.begin(), v.end());
  int cnt = (3 * v[3] - v[0] - v[1] - v[2]);
  int cnt2 = a[26];
  int i = 0;
  if (cnt2 >= cnt) {
    if ((cnt2 - cnt) % 4 == 0) {
      while (a[0] < v[3]) {
        while (s[i] != '?') {
          i++;
        }
        s[i] = 'A';
        a[0]++;
      }
      while (a[2] < v[3]) {
        while (s[i] != '?') {
          i++;
        }
        s[i] = 'C';
        a[2]++;
      }
      while (a['T' - 'A'] < v[3]) {
        while (s[i] != '?') {
          i++;
        }
        s[i] = 'T';
        a['T' - 'A']++;
      }
      while (a['G' - 'A'] < v[3]) {
        while (s[i] != '?') {
          i++;
        }
        s[i] = 'G';
        a['G' - 'A']++;
      }
      int j = 0;
      for (; i < n; i++) {
        if (s[i] == '?') {
          if (j % 4 == 0) {
            s[i] = 'A';
          }
          if (j % 4 == 1) {
            s[i] = 'C';
          }
          if (j % 4 == 2) {
            s[i] = 'G';
          }
          if (j % 4 == 3) {
            s[i] = 'T';
          }
          j++;
        }
      }
      cout << s << endl;
    } else {
      cout << "===\n";
    }
  } else {
    cout << "===\n";
  }
}
