#include <bits/stdc++.h>
int main() {
  int n, x, i, j;
  scanf("%d", &n);
  x = n / 4;
  char s[n];
  int a = 0, c = 0, g = 0, t = 0;
  scanf("%s", &s);
  if (n % 4 != 0) {
    printf("===");
    return 0;
  } else {
    for (i = 0; i < n; i++) {
      if (s[i] == 'A')
        a++;
      else if (s[i] == 'C')
        c++;
      else if (s[i] == 'G')
        g++;
      else if (s[i] == 'T')
        t++;
    }
    if (a > x || c > x || g > x || t > x) {
      printf("===");
      return 0;
    }
    for (j = 0; j < n; j++) {
      if (s[j] == '?') {
        if (a < x) {
          s[j] = 'A';
          a++;
        } else if (c < x) {
          s[j] = 'C';
          c++;
        } else if (g < x) {
          s[j] = 'G';
          g++;
        } else if (t < x) {
          s[j] = 'T';
          t++;
        }
      }
    }
    printf("%s", &s);
    return 0;
  }
}
