#include<iostream>
#include<cstring>
#include<vector>
#include<array>
#include<algorithm>
using namespace std;
using LL = long long;
char dp[41][41][401][2501];

int main(){

#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);

    int n, m;
    cin >> n >> m;
    string s;
    cin >> s;
    dp[0][0][0][0] = 1;
    for(int i = 0; i < n; i++){
        for(int j = 0; j <= i; j++){
            const int mx1 = j * (i - j);
            for(int k = 0; k <= mx1; k++){
                int t = (i + 2 / 3);
                const int mx2 = min(m, t * t * t);
                for(int t = 0; t <= mx2; t++){
                    if (dp[i][j][k][t]){
                        if (s[i] == '?'){
                            dp[i + 1][j + 1][k][t] = 1 | (0 << 1);
                            dp[i + 1][j][j + k][t] = 1 | (1 << 1);
                            dp[i + 1][j][k][t + k] = 1 | (2 << 1);
                            dp[i + 1][j][k][t] = 1 | (3 << 1);
                        }
                        else if (s[i] == 'N'){
                            dp[i + 1][j + 1][k][t] = 1 | (0 << 1);
                        }
                        else if (s[i] == 'A'){
                            dp[i + 1][j][j + k][t] = 1 | (1 << 1);
                        }
                        else if (s[i] == 'C'){
                            dp[i + 1][j][k][t + k] = 1 | (2 << 1);
                        }
                        else{
                            dp[i + 1][j][k][t] = 1 | (3 << 1);
                        }
                    }
                }
            }
        }
    }

    auto get = [&]() -> pair<int, int> {
        for(int i = 0; i <= 40; i++){
            for(int j = 0; j <= 400; j++){
                if (dp[n][i][j][m]){
                    return {i, j};
                }
            }
        }
        return {-1, -1};
    };

    auto [c1, c2] = get();
    if (c1 == -1){
        cout << -1 << '\n';
        return 0;
    }
    int c3 = m;
    string ans;
    for(int i = n; i >= 1; i--){
        int t = dp[i][c1][c2][c3] >> 1;
        if (t == 0){
            ans += "N";
            c1 -= 1;
        }
        else if (t == 1){
            ans += "A";
            c2 -= c1;
        }
        else if (t == 2){
            c3 -= c2;
            ans += "C";
        }
        else ans += "O";
    }
    reverse(ans.begin(), ans.end());
    for(int i = 0; i < n; i++){
        if (s[i] != '?'){
            ans[i] = s[i];
        }
    }
    cout << ans << '\n';

}