#include <bits/stdc++.h>
using namespace std;
// Pura Gente del Coach Moy
using ll = long long;
using pi = pair<int, int>;
using vi = vector<int>;

#define pb push_back
#define SZ(x) ((int)(x).size())
#define ALL(x) begin(x), end(x)
#define FOR(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define ROF(i, a, b) for (int i = (int)a - 1; i >= (int)b; --i)
#define ENDL '\n'

constexpr int MAX = 45;
bitset<2505> dp[MAX][MAX][MAX * MAX];

signed main() {
  cin.tie(0)->sync_with_stdio(0);

  int n, k;
  string s;
  cin >> n >> k >> s;
  dp[0][0][0] = true;
  FOR(i, 0, n) {
    FOR(j, 0, n + 1) {
      FOR(r, 0, n * n + 1) {
        if (s[i] == 'N' || s[i] == '?') dp[i + 1][j + 1][r] |= dp[i][j][r];
        if (s[i] == 'A' || s[i] == '?') dp[i + 1][j][j + r] |= dp[i][j][r];
        if (s[i] == 'C' || s[i] == '?') dp[i + 1][j][r] |= (dp[i][j][r] << r);
        if (s[i] != 'N' && s[i] != 'A' && s[i] != 'C')
          dp[i + 1][j][r] |= dp[i][j][r];
      }
    }
  }

  FOR(i, 0, n + 1) {
    FOR(j, 0, n * n + 1) {
      if (dp[n][i][j][k]) {
        ll p1 = i, p2 = j;
        ROF(idx, n, 0) {
          if (s[idx] == '?') {
            if (p1 && dp[idx][p1 - 1][p2][k]) {
              s[idx] = 'N';
              p1--;
            } else if (p2 >= p1 && dp[idx][p1][p2 - p1][k]) {
              s[idx] = 'A';
              p2 -= p1;
            } else if (k >= p2 && dp[idx][p1][p2][k - p2]) {
              s[idx] = 'C';
              k -= p2;
            } else {
              s[idx] = 'Z';
            }
          } else if (s[idx] == 'N') {
            p1--;
          } else if (s[idx] == 'A') {
            p2 -= p1;
          } else if (s[idx] == 'C') {
            k -= p2;
          }
        }
        cout << s << ENDL;
        return 0;
      }
    }
  }
  cout << -1 << ENDL;

  return 0;
}