#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int counter = 0;
  int comp = 0;
  int a = 0, c = 0, g = 0, t = 0;
  char arr[n];
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }
  if (n % 4 != 0) {
    cout << "===";
    counter++;
  }
  for (int i = 0; i < n; i++) {
    if (arr[i] == 'A')
      a++;
    else if (arr[i] == 'C')
      c++;
    else if (arr[i] == 'G')
      g++;
    else if (arr[i] == 'T')
      t++;
  }
  int maximum = n / 4;
  if ((a > maximum) || (c > maximum) || (g > maximum) || (t > maximum)) {
    if (counter == 0) {
      cout << "===";
      counter++;
    }
  }
  int ar = maximum - a;
  int cr = maximum - c;
  int gr = maximum - g;
  int tr = maximum - t;
  if (a < maximum) {
    for (int i = 0; i < n; i++) {
      if (arr[i] == '?') {
        arr[i] = 'A';
        comp++;
        if (comp == ar) {
          comp = 0;
          break;
        }
      }
    }
  }
  if (c < maximum) {
    for (int i = 0; i < n; i++) {
      if (arr[i] == '?') {
        arr[i] = 'C';
        comp++;
        if (comp == cr) {
          comp = 0;
          break;
        }
      }
    }
  }
  if (g < maximum) {
    for (int i = 0; i < n; i++) {
      if (arr[i] == '?') {
        arr[i] = 'G';
        comp++;
        if (comp == gr) {
          comp = 0;
          break;
        }
      }
    }
  }
  if (t < maximum) {
    for (int i = 0; i < n; i++) {
      if (arr[i] == '?') {
        arr[i] = 'T';
        comp++;
        if (comp == tr) {
          comp = 0;
          break;
        }
      }
    }
  }
  if (counter == 0) {
    for (int i = 0; i < n; i++) {
      cout << arr[i];
    }
  }
}
