#include <bits/stdc++.h>

using namespace std;
using tpl = tuple<int, int, int, int>;

const int N = 45, M = 405, MAXK = 2510;

int n, k, cnt;
string s;
bitset<MAXK> dp[N][N][M];
tpl tp;
bool flag;

void print(tpl x) {
    auto [i, j, t, p] = x;
    if (!i) return ;
    if ((s[i] == 'N' || s[i] == '?') && j && dp[i - 1][j - 1][t][p]) {
        print({i - 1, j - 1, t, p}), cout << 'N';
    } else if ((s[i] == 'A' || s[i] == '?') && t >= j && dp[i - 1][j][t - j][p]) {
        print({i - 1, j, t - j, p}), cout << 'A';
    } else if ((s[i] == 'C' || s[i] == '?') && p >= t && dp[i - 1][j][t][p - t]) {
        print({i - 1, j, t, p - t}), cout << 'C';
    } else if (s[i] != 'N' && s[i] != 'A' && s[i] != 'C' && dp[i - 1][j][t][p]) {
        print({i - 1, j, t, p}), cout << (s[i] == '?' ? 'B' : s[i]);
    }
}

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    cin >> n >> k >> s, s = ' ' + s;
    dp[0][0][0][0] = 1;
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j < i; j++) {
            for (int t = 0; t <= (i - 1) * i / 4; t++) {
                if (s[i] == 'N' || s[i] == '?') dp[i][j + 1][t] |= dp[i - 1][j][t];
                if (s[i] == 'A' || s[i] == '?') if (t + j < M) dp[i][j][t + j] |= dp[i - 1][j][t];
                if (s[i] == 'C' || s[i] == '?') dp[i][j][t] |= (dp[i - 1][j][t] << t);
                if (s[i] != 'N' && s[i] != 'A' && s[i] != 'C') dp[i][j][t] |= dp[i - 1][j][t];
            }
        }
        if (i == n) {
            for (int j = 0; j <= i; j++) {
                for (int t = 0; t <= (i + 1) * i / 4; t++) {
                    if (dp[i][j][t][k]) flag = 1, tp = {i, j, t, k};
                }
            }
        }
    }
    if (!flag) cout << -1;
    else print(tp);
    return 0;
}