#include <bits/stdc++.h>
const char nl = '\n';
using namespace std;
using ll = long long;
using ld = long double;
const int R = 41, P = 2367, Q = 401;

char dp[R][P][Q][R];

int main() {
  cin.tie(0)->sync_with_stdio(0);
  //cerr << sizeof(dp) << nl; return 0;
  // dp[pos][NAC][NA][N]
  int n, k; cin >> n >> k;
  string s; cin >> s;
  if (k >= P) {
    cout << "-1\n";
    return 0;
  }
  dp[0][0][0][0] = 1;
  //int cnt = 0;
  for (int i = 0; i < n; i++) {
    for (int NAC = 0; NAC <= k; NAC++) {
      for (int NA = 0; NA <= (i+1)/2*(i/2); NA++) {
        for (int N = 0; N <= i; N++) {
          //cnt++;
          if (!dp[i][NAC][NA][N]) continue;
          if (s[i] == '?') {
            // N
            dp[i+1][NAC][NA][N+1] = 1;
            // A
            dp[i+1][NAC][NA+N][N] = 1;
            // C
            dp[i+1][NAC+NA][NA][N] = 1;
            // B
            dp[i+1][NAC][NA][N] = 1;
          } else if (s[i] == 'N') {
            dp[i+1][NAC][NA][N+1] = 1;
          } else if (s[i] == 'A') {
            dp[i+1][NAC][NA+N][N] = 1;
          } else if (s[i] == 'C') {
            dp[i+1][NAC+NA][NA][N] = 1;
          } else {
            dp[i+1][NAC][NA][N] = 1;
          }
        }
      }
    }
  }
  //cerr << cnt << nl;
  int NAC = k, NA = -1, N = -1;
  for (int i = 0; i < Q; i++) {
    for (int j = 0; j < R; j++) {
      if (dp[n][NAC][i][j]) {
        NA = i;
        N = j;
        break;
      }
    }
  }
  if (NA == -1) {
    cout << "-1\n";
    return 0;
  }
  string ans;
  for (int i = n-1; i >= 0; i--) {
    if (s[i] == '?') {
      if (N > 0 && dp[i][NAC][NA][N-1]) {
        ans.push_back('N');
        N--;
      } else if (NA >= N && dp[i][NAC][NA-N][N]) {
        ans.push_back('A');
        NA -= N;
      } else if (NAC >= NA && dp[i][NAC-NA][NA][N]) {
        ans.push_back('C');
        NAC -= NA;
      } else {
        assert(dp[i][NAC][NA][N]);
        ans.push_back('B');
      }
    } else if (s[i] == 'N') {
      assert(N > 0);
      ans.push_back('N');
      N--;
    } else if (s[i] == 'A') {
      assert(NA >= N);
      ans.push_back('A');
      NA -= N;
    } else if (s[i] == 'C') {
      assert(NAC >= NA);
      ans.push_back('C');
      NAC -= NA;
    } else {
      ans.push_back(s[i]);
    }
  }
  reverse(begin(ans), end(ans));
  cout << ans << nl;
}