#include <bits/stdc++.h>

using namespace std;

const int N = 45, M = 2501;

bitset<M> f[N][N][N];

int main() {
  cin.tie(0)->sync_with_stdio(0);
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  s = '\0' + s;
  for (int i = 0; i <= n; i++) f[0][0][i].set(0);
  auto transN = [&](int i, int j, int k) {
    f[i + 1][j + 1][k] |= f[i][j][k];
  };
  auto transA = [&](int i, int j, int k) {
    f[i + 1][j][k] |= f[i][j][k] << (j * k);
  };
  auto transC = [&](int i, int j, int k) {
    if (k > 0) f[i + 1][j][k - 1] |= f[i][j][k];
  };
  auto transO = [&](int i, int j, int k) {
    f[i + 1][j][k] |= f[i][j][k];
  };
  auto transP = [&](int i, int j, int k) {
    transN(i, j, k);
    transA(i, j, k);
    transC(i, j, k);
    transO(i, j, k);
  };
  for (int i = 0; i < n; i++) {
    for (int j = 0; j <= n; j++) {
      for (int k = 0; k <= n; k++) {
        if (s[i + 1] == 'N') transN(i, j, k);
        else if (s[i + 1] == 'A') transA(i, j, k);
        else if (s[i + 1] == 'C') transC(i, j, k);
        else if (s[i + 1] == '?') transP(i, j, k);
        else transO(i, j, k);
      }
    }
  }
  auto print = [&](int c) {
    string ans; ans.resize(n);
    for (int i = n, j = c, l = 0, now = k; i >= 1; i--) {
      if ((s[i] == 'N' || s[i] == '?') && j > 0 && f[i - 1][j - 1][l][now]) ans[i - 1] = 'N', j--;
      else if ((s[i] == 'A' || s[i] == '?') && now >= j * l && f[i - 1][j][l][now - j * l]) ans[i - 1] = 'A', now -= j * l;
      else if ((s[i] == 'C' || s[i] == '?') && f[i - 1][j][l + 1][now]) ans[i - 1] = 'C', l++;
      else ans[i - 1] = s[i] == '?' ? 'Z' : s[i]; 
    }
    cout << ans << '\n';
  };
  for (int i = 0; i <= n; i++) {
    if (f[n][i][0][k]) {
      print(i);
      return 0;
    }
  }
  cout << -1 << '\n';
  return 0;
}