#include <bits/stdc++.h>
using namespace std;
int n, a, b, c, d, e, len, fuck, pps;
char st[1000];
int main() {
  cin >> n;
  scanf("%s", st + 1);
  len = strlen(st + 1);
  for (int i = 1; i <= len; i++) {
    if (st[i] == 'A') a++;
    if (st[i] == 'G') b++;
    if (st[i] == 'C') c++;
    if (st[i] == 'T') d++;
    if (st[i] == '?') e++;
  }
  len = 0;
  len = max(len, a);
  len = max(len, b);
  len = max(len, c);
  len = max(len, d);
  a = len - a, b = len - b, c = len - c, d = len - d;
  if (e < a + b + c + d || (e - a - b - c - d) % 4 != 0)
    puts("===");
  else {
    fuck = (e - a - b - c - d) / 4;
    len = strlen(st + 1);
    pps = 0;
    for (int i = 1; i <= len; i++) {
      if (st[i] == '?') {
        if (a)
          a--, st[i] = 'A';
        else if (b)
          b--, st[i] = 'G';
        else if (c)
          c--, st[i] = 'C';
        else if (d)
          d--, st[i] = 'T';
        else {
          pps = pps % 4 + 1;
          if (pps == 1) st[i] = 'A';
          if (pps == 2) st[i] = 'G';
          if (pps == 3) st[i] = 'C';
          if (pps == 4) st[i] = 'T';
        }
      }
    }
    printf("%s", st + 1);
  }
  return 0;
}
