#include <bits/stdc++.h>
using namespace std;
int main() {
  int len, check, i, x[10], highest = 0, pos = 0, needed = 0, ok, new_val = 0,
                            go = 0;
  fill(x, x + 10, 0);
  string s;
  cin >> len >> s;
  if (len % 4 == 0) {
    for (i = 0; i < len; i++) {
      if (s[i] == 'A') {
        x[0]++;
      }
      if (s[i] == 'C') {
        x[1]++;
      }
      if (s[i] == 'G') {
        x[2]++;
      }
      if (s[i] == 'T') {
        x[3]++;
      }
      if (s[i] == '?') {
        x[4]++;
      }
    }
    new_val = len / 4;
    for (i = 0; i < 4; i++) {
      x[i] = new_val - x[i];
      if (x[i] < 0) {
        go = 1;
      }
    }
    if (go == 0) {
      for (i = 0; i < len; i++) {
        if (s[i] == '?' && x[0] > 0) {
          s[i] = 'A';
          x[0]--;
        }
        if (s[i] == '?' && x[1] > 0) {
          s[i] = 'C';
          x[1]--;
        }
        if (s[i] == '?' && x[2] > 0) {
          s[i] = 'G';
          x[2]--;
        }
        if (s[i] == '?' && x[3] > 0) {
          s[i] = 'T';
          x[3]--;
        }
      }
      cout << s << endl;
    } else {
      cout << "===" << endl;
    }
  } else {
    cout << "===" << endl;
  }
  return 0;
}
