#include <bits/stdc++.h>
using namespace std;
long long n;
string s;
void no() {
  cout << "===";
  exit(0);
}
void solve() {
  cin >> n >> s;
  if (n % 4) no();
  long long ka = 0, kg = 0, kc = 0, kt = 0, kq = 0;
  for (long long i = 0; i < (n); ++i) {
    if (s[i] == 'A')
      ++ka;
    else if (s[i] == 'G')
      ++kg;
    else if (s[i] == 'C')
      ++kc;
    else if (s[i] == 'T')
      ++kt;
    else if (s[i] == '?')
      ++kq;
  }
  ka = n / 4 - ka;
  kg = n / 4 - kg;
  kc = n / 4 - kc;
  kt = n / 4 - kt;
  if (ka < 0 || kg < 0 || kc < 0 || kt < 0) no();
  if (ka + kg + kt + kc > kq) no();
  for (long long i = 0; i < (n); ++i) {
    if (s[i] == '?') {
      if (ka)
        s[i] = 'A', --ka;
      else if (kg)
        s[i] = 'G', --kg;
      else if (kt)
        s[i] = 'T', --kt;
      else if (kc)
        s[i] = 'C', --kc;
    }
  }
  cout << s;
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  solve();
  return 0;
}
