#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

int c3(int x) { return x * (x - 1) * (x - 2) / 6; }
int c2(int x) { return x * (x - 1) / 2; }

int main() {
  cin.tie(0)->sync_with_stdio(0);
  int n, kk;
  string s;
  cin >> n >> kk >> s;
  vector dp(n + 1, vector(1, vector(1, vector(1, '\1'))));
  rep(i, 0, n) {
    dp[i + 1] = vector(min(kk, c3(i + 1)) + 1, vector(c2(i + 1) + 1, vector(i + 1 + 1, '\0')));
    rep(j, 0, min(kk, c3(i)) + 1) rep(k, 0, c2(i) + 1) rep(l, 0, i + 1) {
      if (dp[i][j][k][l] == '\0') continue;
      if (s[i] == 'N' || s[i] == '?') {
        dp[i + 1][j][k][l + 1] = 'N';
      }
      if (s[i] == 'A' || s[i] == '?') {
        dp[i + 1][j][k + l][l] = 'A';
      }
      if (s[i] == 'C' || s[i] == '?') {
        if (j + k <= kk) dp[i + 1][j + k][k][l] = 'C';
      }
      if (s[i] != 'N' && s[i] != 'A' && s[i] != 'C') {
        dp[i + 1][j][k][l] = s[i];
      }
    }
  }
  if (kk >= sz(dp[n])) {
    cout << "-1\n";
    return 0;
  }
  int i = n, j = kk, k = -1, l = -1;
  rep(x, 0, sz(dp[i][j])) rep(y, 0, sz(dp[i][j][x])) {
    if (dp[i][j][x][y] != '\0') {
      k = x;
      l = y;
      break;
    }
  }
  if (k == -1) {
    cout << "-1\n";
    return 0;
  }
  string ans;
  while (i > 0) {
    ans.push_back(dp[i][j][k][l]);
    if (ans.back() == '?') ans.back() = 'X';
    int ni, nj, nk, nl;
    if (ans.back() == 'N') {
      ni = i - 1;
      nj = j;
      nk = k;
      nl = l - 1;
    } else if (ans.back() == 'A') {
      ni = i - 1;
      nj = j;
      nk = k - l;
      nl = l;
    } else if (ans.back() == 'C') {
      ni = i - 1;
      nj = j - k;
      nk = k;
      nl = l;
    } else {
      ni = i - 1;
      nj = j;
      nk = k;
      nl = l;
    }
    i = ni;
    j = nj;
    k = nk;
    l = nl;
  }
  reverse(all(ans));
  cout << ans << '\n';
}