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

int f[45][45][45][2505];
string s;
int n, k;


void print(int n, int a, int b, int t) {
    if (n == 0) return;
    if (f[n][a][b][t] == 0) {
        print(n - 1, a, b, t);
        if (s[n] != '?') cout << s[n];
        else cout << "B";
    } else if (f[n][a][b][t] == 1) {
        print(n - 1, a - 1, b, t);
        cout << "N";
    } else if (f[n][a][b][t] == 2) {
        print(n - 1, a, b, t - a * b);
        cout << "A";
    } else if (f[n][a][b][t] == 3) {
        print(n - 1, a, b + 1, t);
        cout << "C";
    }
}

void DoN(int i) {
    for (int a = 0; a < i; a++) {
        for (int b = 0; b <= n - i; b++) {
            for (int t = 0; t <= k; t++) {
                if (f[i - 1][a][b][t] != -1) {
                    f[i][a + 1][b][t] = 1;
                }
            }
        }
    }
}

void DoA(int i) {
    for (int a = 0; a < i; a++) {
        for (int b = 0; b <= n - i; b++) {
            for (int t = 0; t <= k; t++) {
                if (f[i - 1][a][b][t] != -1) {
                    f[i][a][b][min(t + a * b, k + 1)] = 2;
                }
            }
        }
    }  
}

void DoC(int i) {
    for (int a = 0; a < i; a++) {
        for (int b = 1; b <= n - i + 1; b++) {
            for (int t = 0; t <= k; t++) {
                if (f[i - 1][a][b][t] != -1) {
                    f[i][a][b - 1][t] = 3;
                }
            }
        }
    }         
}

void DoNull(int i) {
    for (int a = 0; a < i; a++) {
        for (int b = 0; b <= n - i; b++) {
            for (int t = 0; t <= k; t++) {
                if (f[i - 1][a][b][t] != -1) {
                    f[i][a][b][t] = 0;
                }
            }
        }
    }  
}

signed main() {
    cin >> n >> k;
    cin >> s;
    s = ' ' + s;
    memset(f, -1, sizeof(f));
    for(int i = 0; i <= n; i++) {
        f[0][0][i][0] = 0;
    }
    for (int i = 1; i <= n; i++) {
        if (s[i] == '?') {            
            DoN(i);
            DoA(i);
            DoC(i);
            DoNull(i);
        } else if (s[i] == 'N') {
            DoN(i);            
        } else if (s[i] == 'A') {
            DoA(i);       
        } else if (s[i] == 'C') {
            DoC(i);
        } else {
            DoNull(i);
        }
    }
    for (int a = 0; a <= n; a++) {
        if (f[n][a][0][k] != -1) {
            print(n, a, 0, k);
            return 0;
        }
    }
    puts("-1");
    return 0;
}