#include<bits/stdc++.h>
using namespace std;
#define i64 long long
#define i128 __int128
#define mp make_pair
#define pb push_back
#define all(x) (x).begin(), (x).end()
bitset<2501> f[42][42][42];
void Solve(void) {
  int N, K; cin >> N >> K;
  string S; cin >> S; S = " " + S;
  for (int c = 0; c <= N; c ++) {
    f[0][0][c].set(0);
  }
  for (int i = 1; i <= N; i ++) {
    if (S[i] == 'N' || S[i] == '?') {
      for (int n = 1; n <= i; n ++) {
        for (int c = 0; c <= N - i; c ++) {
          f[i][n][c] |= f[i - 1][n - 1][c];
        }
      }
    } if (S[i] == 'A' || S[i] == '?') {
      for (int n = 0; n <= i; n ++) {
        for (int c = 0; c <= N - i; c ++) {
          f[i][n][c] |= (f[i - 1][n][c] << (n * c));
        }
      }
    } if (S[i] == 'C' || S[i] == '?') {
      for (int n = 0; n <= i; n ++) {
        for (int c = 0; c <= N - i; c ++) {
          f[i][n][c] |= (f[i - 1][n][c + 1]);
        }
      }
    } if (S[i] == '?' || (S[i] != 'N' && S[i] != 'A' && S[i] != 'C')) {
      for (int n = 0; n <= i; n ++) {
        for (int c = 0; c <= N - i; c ++) {
          f[i][n][c] |= f[i - 1][n][c];
        }
      }
    }
  }
  
  auto Trace = [&] (int p, int n, int c, int k) {
    vector<char> ans;
    while (p) {
      if (S[p] != '?') {
        if (S[p] == 'A') {
          ans.pb('A'); p --; k -= (n * c);
        } else if (S[p] == 'N') {
          ans.pb('N'); p --; n --;
        } else if (S[p] == 'C') {
          ans.pb('C'); p --; c ++;
        } else {
          ans.pb(S[p]); p --;
        }
      } else {
        if (n && f[p][n][c][k] == f[p - 1][n - 1][c][k]) {
          ans.pb('N'); p --; n --;
        } else if (k >= n * c && f[p][n][c][k] == f[p - 1][n][c][k - n * c]) {
          ans.pb('A'); p --; k -= n * c;
        } else if (c <= N - p && f[p][n][c][k] == f[p - 1][n][c + 1][k]) {
          ans.pb('C'); p --; c ++;
        } else if (f[p][n][c][k] == f[p - 1][n][c][k]) {
          ans.pb('D'); p --;
        }
      }
    }
    reverse(all(ans));
    for (auto c : ans) cout << c;
  };

  for (int n = 0; n <= N; n ++) {
    if (f[N][n][0][K]) {
      // cout << n << " " << f[N][n][0][K] << "\n";
      Trace(N, n, 0, K);
      return; 
    }
  }
  cout << -1 << "\n";
}
signed main() {
  ios_base::sync_with_stdio(false); cin.tie(0);
  int Tests = 1; // cin >> Tests;
  while (Tests --) {
    Solve();
  }
}