#include <bits/stdc++.h>
using namespace std;
template <class c>
struct rge {
  c b, e;
};
template <class c>
rge<c> range(c i, c j) {
  return rge<c>{i, j};
}
template <class c>
auto dud(c* x) -> decltype(cerr << *x, 0);
template <class c>
char dud(...);
struct debug {
  template <class c>
  debug& operator<<(const c&) {
    return *this;
  }
};
const long long int N = 2e5 + 10;
long long int mod = 1e9 + 7;
long long int dx[4] = {0, 0, +1, -1};
long long int dy[4] = {+1, -1, 0, 0};
long long int po(long long int a, long long int b) {
  a %= mod;
  long long int res = 1;
  while (b > 0) {
    if (b & 1) res = (res * a) % mod;
    a = (a * a) % mod;
    b >>= 1;
  }
  return res;
}
long long int a, c, g, tt;
void solve() {
  long long int n;
  cin >> n;
  string s;
  cin >> s;
  if (n % 4 != 0) {
    cout << "===\n";
    return;
  }
  long long int mv = n / 4;
  for (long long int 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')
      tt++;
  }
  long long int rem = n - a - c - g - tt;
  if (a > mv || c > mv || g > mv || tt > mv) {
    cout << "===\n";
    return;
  }
  long long int want = (mv - a) + (mv - c) + (mv - g) + mv - tt;
  if (want > rem) {
    cout << "===\n";
    return;
  }
  a = mv - a;
  g = mv - g;
  c = mv - c;
  tt = mv - tt;
  for (long long int i = 0; i < n; i++) {
    if (s[i] == '?') {
      if (a > 0) {
        s[i] = 'A';
        a--;
      } else if (g > 0) {
        s[i] = 'G';
        g--;
      } else if (c > 0) {
        s[i] = 'C';
        c--;
      } else if (tt > 0) {
        s[i] = 'T';
        tt--;
      }
    }
  }
  cout << s << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long int t = 1;
  while (t--) solve();
  return 0;
}
