#include <bits/stdc++.h>
using namespace std;
char A[300];
int cnt[5];
char data[5] = "ACGT";
int main() {
  int n;
  scanf("%d", &n);
  scanf("%s", A);
  for (int i = 0; A[i]; i++) {
    if (A[i] == 'A')
      cnt[0]++;
    else if (A[i] == 'C')
      cnt[1]++;
    else if (A[i] == 'G')
      cnt[2]++;
    else if (A[i] == 'T')
      cnt[3]++;
    else
      cnt[4]++;
  }
  int big = 0, dif = 0;
  ;
  for (int i = 0; i < 4; i++) big = max(big, cnt[i]);
  for (int i = 0; i < 4; i++) {
    cnt[i] = big - cnt[i];
    dif += cnt[i];
  }
  if (dif > cnt[4]) {
    printf("===");
    return 0;
  }
  if ((cnt[4] - dif) % 4 != 0) {
    printf("===");
    return 0;
  }
  int flag = 0;
  for (int i = 0; A[i]; i++) {
    if (A[i] == '?') {
      flag = 0;
      for (int j = 0; j < 4; j++) {
        if (cnt[j] > 0) {
          A[i] = data[j];
          cnt[j]--;
          flag = 1;
          break;
        }
      }
      if (flag == 0) {
        for (int j = 0; j < 4; j++) cnt[j]++;
        i--;
      }
    }
  }
  printf("%s", A);
}
