#include <cstdio>
#include <bitset>
#include <string>
#include <iostream>
#include <algorithm>

using i64 = long long;

const int N = 45;
const int K = 2505;

int n, k;
std::string s;
std::bitset<K> f[N][N][N];

std::string ans;

void GetString(int i, int j, int k, int l){
	if (i == 0) {
		return;
	}
	if (ans[i - 1] == '?') {
		if (j > 0 && f[i - 1][j - 1][k][l]) {
			ans[i - 1] = 'N';
			GetString(i - 1, j - 1, k, l);
		} else if (k < n && f[i - 1][j][k + 1][l]) {
			ans[i - 1] = 'C';
			GetString(i - 1, j, k + 1, l);
		} else if (l >= j * k && f[i - 1][j][k][l - j * k]) {
			ans[i - 1] = 'A';
			GetString(i - 1, j, k, l - j * k);
		} else {
			ans[i - 1] = 'O';
			GetString(i - 1, j, k, l);
		}
	} else {
		GetString(i - 1, j - (ans[i - 1] == 'N'), k + (ans[i - 1] == 'C'), l - (ans[i - 1] == 'A') * (j * k));
	}
}

int main(){
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);

	std::cin >> n >> k;
	std::cin >> s;

	for (int i = 0; i <= n; i++) {
		f[0][0][i][0] = true;
	}

	for (int i = 1; i <= n; i++) {
		for (int j = 0; j <= n; j++) {
			for (int l = 0; l <= n; l++) {
				if (s[i - 1] != 'A' && s[i - 1] != 'N' && s[i - 1] != 'C') {
					f[i][j][l] |= f[i - 1][j][l];
				}
				if (s[i - 1] == 'N' || s[i - 1] == '?') {
					f[i][j + 1][l] |= f[i - 1][j][l];
				}
				if (s[i - 1] == 'C' || s[i - 1] == '?') {
					f[i][j][l] |= f[i - 1][j][l + 1]; 
				}
				if (s[i - 1] == 'A' || s[i - 1] == '?') {
					f[i][j][l] |= (f[i - 1][j][l] << (j * l));
				}
			}
		}
	}

	for (int i = 0; i <= n; i++) {
		if (f[n][i][0][k]) {
			ans = s;
			GetString(n, i, 0, k);
			std::cout << ans;
			return 0;
		}
	}

	std::cout << -1;
	return 0;
}