#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int a, ca = 0, cc = 0, ct = 0, cg = 0, co = 0, x = 0, y = 0, pup = 0;
  string s;
  cin >> a >> s;
  if ((a % 2) == 0 && (a % 4) == 0) {
    for (int i = 0; i < a; ++i) {
      if (s.at(i) == 'A') {
        ca++;
      }
      if (s.at(i) == 'C') {
        cc++;
      }
      if (s.at(i) == 'G') {
        cg++;
      }
      if (s.at(i) == 'T') {
        ct++;
      }
      if (s.at(i) == '?') {
        co++;
      }
    }
    x = a / 4;
    if (ca > x || cc > x || cg > x || ct > x) {
      cout << "===\n";
      goto kok;
    }
    ca = x - ca;
    cc = x - cc;
    cg = x - cg;
    ct = x - ct;
    for (int i = 0; i < a; ++i) {
      if (s.at(i) == '?') {
        if (ca > 0) {
          ca--;
          s.at(i) = 'A';
          goto pol;
        }
        if (cc > 0) {
          cc--;
          s.at(i) = 'C';
          goto pol;
        }
        if (cg > 0) {
          cg--;
          s.at(i) = 'G';
          goto pol;
        }
        if (ct > 0) {
          ct--;
          s.at(i) = 'T';
          goto pol;
        }
      }
    pol:;
    }
    cout << s << "\n";
  } else {
    cout << "===\n";
    goto kok;
  }
kok:;
  return 0;
}
