#include <bits/stdc++.h>

using namespace std;

#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define RFOR(i, a, b) for(int i = (a) - 1; i >= (b); i--)
#define SZ(a) int(a.size())
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair
#define F first
#define S second

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef double db;

const int M = 42;
const int M2 = 407;
const int K = 2547;

bitset<K> dp[M][M][M2];

int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	int n, k;
	string s;
	cin >> n >> k >> s;
	dp[0][0][0].set(0);
	FOR(i, 0, n)
	{
		FOR(N, 0, i + 1)
		{
			FOR(NA, 0, M2)
			{
				if (s[i] == '?' || s[i] == 'N')
					dp[i + 1][N + 1][NA] |= dp[i][N][NA];
				if ((s[i] == '?' || s[i] == 'A') && NA + N < M2)
					dp[i + 1][N][NA + N] |= dp[i][N][NA];
				if (s[i] == '?' || s[i] == 'C')
					dp[i + 1][N][NA] |= dp[i][N][NA] << NA;
				if (s[i] != 'N' && s[i] != 'A' && s[i] != 'C')
					dp[i + 1][N][NA] |= dp[i][N][NA];
			}
		}
	}
	int N = -1, NA = -1;
	FOR(j, 0, M)
		FOR(l, 0, M2)
			if (dp[n][j][l][k])
			{
				N = j;
				NA = l;
				break;
			}
	cerr << N << " " << NA << endl;
	if (N == -1)
	{
		cout << "-1\n";
		return 0;
	}
	string ans;
	RFOR(i, n, 0)
	{
		if ((s[i] == '?' || s[i] == 'N') && N - 1 >= 0 && dp[i][N - 1][NA][k])
		{
			ans += 'N';
			N--;
		}
		else if ((s[i] == '?' || s[i] == 'A') && NA - N >= 0 && dp[i][N][NA - N][k])
		{
			ans += 'A';
			NA -= N;
		}
		else if ((s[i] == '?' || s[i] == 'C') && k - NA >= 0 && dp[i][N][NA][k - NA])
		{
			ans += 'C';
			k -= NA;
		}
		else if (s[i] != 'N' && s[i] != 'A' && s[i] != 'C' && dp[i][N][NA][k])
		{
			ans += 'B';
		}
		else
		{
			assert(false);
		}
	}
	assert(N == 0 && NA == 0 && k == 0);
	reverse(ALL(ans));
	cout << ans << "\n";
	return 0;
}