#include <bits/stdc++.h>
using namespace std;
#define MAXN 45
#define MAXK 2505

int n, k, p, m;
string s, t;
bitset<MAXK> f[MAXN][MAXN][MAXN];

signed main(){
	// ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);

	cin >> n >> m >> s; s = ' ' + s; for (int i(0); i<=n; ++i) f[0][0][i].set(0);
	for (int i(1); i<=n; ++i){
		for (int j(0); j<=i; ++j) for (int k(0); k<=n-i; ++k){
			if (s[i] == 'N' || s[i] == '?') if (j) f[i][j][k] |= f[i-1][j-1][k];
			if (s[i] == 'A' || s[i] == '?') f[i][j][k] |= f[i-1][j][k] << (j*k);
			if (s[i] == 'C' || s[i] == '?') f[i][j][k] |= f[i-1][j][k+1];
			if (s[i] != 'N' && s[i] != 'C' && s[i] != 'A') f[i][j][k] |= f[i-1][j][k];
		}
 	}
	while (p <= n && !f[n][p][0][m]) ++p;
	if (p > n){cout << -1; return 0;}
	// cout << "I AK IOI\n";

	t.resize(n+1);
	for (int i(n), j(p), k(0), l(m); i; --i){
		if (s[i] == 'N' || (s[i] == '?' && j && f[i-1][j-1][k][l])){--j; t[i] = 'N';}
		else if (s[i] == 'C' || (s[i] == '?' && f[i-1][j][k+1][l])){++k; t[i] = 'C';}
		else if (s[i] == 'A' || (s[i] == '?' && l >= j*k && f[i-1][j][k][l-j*k])){l -= j*k; t[i] = 'A';}
		else t[i] = (s[i] == '?' ? 'B' : s[i]);
		// cout << i << ' ' << j << ' '
	}
	cout << t.substr(1, n);

	return 0;
}