#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int p, i, aa = 0, tt = 0, cc = 0, gg = 0, sum = 0;
  cin >> p >> s;
  for (i = 0; i < s.size(); i++) {
    if (s[i] == 'A')
      aa++;
    else if (s[i] == 'T')
      tt++;
    else if (s[i] == 'G')
      gg++;
    else if (s[i] == 'C')
      cc++;
    else if (s[i] == '?')
      sum++;
  }
  if (sum == 0) {
    if (aa == tt && tt == gg && gg == cc)
      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 ((aa + tt) < (gg + cc)) {
          if (aa > tt) {
            s[i] = 'T';
            tt++;
          } else {
            s[i] = 'A';
            aa++;
          }
        } else {
          if (gg > cc) {
            s[i] = 'C';
            cc++;
          } else {
            s[i] = 'G';
            gg++;
          }
        }
      }
    }
    if (aa == tt && tt == gg && gg == cc)
      cout << s << endl;
    else
      cout << "===" << endl;
    return 0;
  }
}
