#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define all(x) begin(x), end(x)
#define sz(x) int((x).size())
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

#ifdef LOCAL
auto operator<<(auto& o, auto x) -> decltype(x.first, o);
auto operator<<(auto& o, auto x) -> decltype(x.end(), o) {
  o << "{";
  for (int i = 0; auto y : x) o << ", " + !i++ * 2 << y;
  return o << "}";
}
auto operator<<(auto& o, auto x) -> decltype(x.first, o) {
  return o << "(" << x.first << ", " << x.second << ")";
}
void __print(auto... x) { ((cerr << x << " "), ...) << endl; }
#define debug(x...) __print("[" #x "]:", x)
#else
#define debug(...) 2137
#endif

using B = bitset<2501>;
const int N = 44;
B dp[N][N * N][N]; // pref, na, n, (nac)

int main() {
  cin.tie(0)->sync_with_stdio(0);
  int n, k;
  string s;
  cin >> n >> k >> s;
  dp[0][0][0][0] = 1;
  rep(p, 0, n) rep(i, 0, p * p + 1) rep(j, 0, p + 1) {
    if (s[p] == 'N' || s[p] == '?') dp[p + 1][i][j + 1] |= dp[p][i][j];
    if (s[p] == 'A' || s[p] == '?') dp[p + 1][i + j][j] |= dp[p][i][j];
    if (s[p] == 'C' || s[p] == '?') dp[p + 1][i][j] |= dp[p][i][j] << i;
    if (s[p] != 'N' && s[p] != 'A' && s[p] != 'C') dp[p + 1][i][j] |= dp[p][i][j];
  }
  int x = -1, y = -1;
  rep(i, 0, n * n + 1) rep(j, 0, n + 1) if (dp[n][i][j][k]) {
    x = i;
    y = j;
    break;
  }
  if (x == -1) {
    cout << "-1\n";
    return 0;
  }
  string ans;
  int i = n;
  while (i > 0) {
    debug(i, x, y, k);
    char c = s[i - 1];
    if ((c == 'N' || c == '?') && dp[i - 1][x][y - 1][k]) {
      ans += 'N';
      i--;
      y--;
    } else if ((c == 'A' || c == '?') && x >= y && dp[i - 1][x - y][y][k]) {
      ans += 'A';
      i--;
      x -= y;
    } else if ((c == 'C' || c == '?') && k >= x && dp[i - 1][x][y][k - x]) {
      ans += 'C';
      i--;
      k -= x;
    } else {
      i--;
      ans += c == '?' ? 'Z' : c;
    }
  }
  reverse(all(ans));
  cout << ans << '\n';
}