#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int n, i, a = 0, t = 0, c = 0, g = 0, su = 0;
  cin >> n >> s;
  for (i = 0; i < s.size(); i++) {
    if (s[i] == 'A')
      a++;
    else if (s[i] == 'T')
      t++;
    else if (s[i] == 'G')
      g++;
    else if (s[i] == 'C')
      c++;
    else if (s[i] == '?')
      su++;
  }
  if (su == 0) {
    if (a == t && t == g && g == c)
      cout << s << endl;
    else
      cout << "===" << endl;
  } else {
    for (i = 0; i < s.size(); i++) {
      if (s[i] == 'A' || s[i] == 'T' || s[i] == 'G' || s[i] == 'C')
        continue;
      else if (s[i] == '?') {
        if ((a + t) < (g + c)) {
          if (a > t) {
            s[i] = 'T';
            t++;
          } else {
            s[i] = 'A';
            a++;
          }
        } else {
          if (g > c) {
            s[i] = 'C';
            c++;
          } else {
            s[i] = 'G';
            g++;
          }
        }
      }
    }
    if (a == t && t == g && g == c)
      cout << s << endl;
    else
      cout << "===" << endl;
    return 0;
  }
}
