#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define pb push_back
#define all(a) a.begin(), a.end()
#define sz(a) ((int)a.size())
const int mod = 1e9 + 7, N = 100000;

bitset <2501> dp[41][41][401];

int main() {
	ios::sync_with_stdio(false), cin.tie(0);
	int n, t;
	cin >> n >> t;
	string s; cin >> s;
	dp[0][0][0][0] = true;
	int mxN = 0, mxNA = 0;
	for (int i = 0; i < n; ++i) {
		int nxtN = mxN, nxtNA = mxNA;
		for (int j = 0; j <= mxN; ++j) for (int k = 0; k <= mxNA; ++k) if (dp[i][j][k].any()) {
			if (s[i] == 'N' || s[i] == '?') {
				dp[i + 1][j + 1][k] |= dp[i][j][k];
				nxtN = max(nxtN, j + 1);
			}
			if (s[i] == 'A' || s[i] == '?') {
				dp[i + 1][j][k + j] |= dp[i][j][k];
				nxtNA = max(nxtNA, k + j);
			}
			if (s[i] == 'C' || s[i] == '?') {
				dp[i + 1][j][k] |= dp[i][j][k] << k;
			}
			if (s[i] != '?' && (s[i] != 'N' && s[i] != 'A' && s[i] != 'C')) {
				dp[i + 1][j][k] |= dp[i][j][k];
			}
		}
		mxN = nxtN, mxNA = nxtNA;
	}

	int x = -1, y = -1, z = t;
	for (int i = 0; i <= mxN; ++i) for (int j = 0; j <= mxNA; ++j) if (dp[n][i][j][t]) {
		x = i, y = j;
		break;
	}
	if (x == -1) {
		cout << "-1\n";
		return 0;
	}
	string ans = s;
	for (int i = n - 1; ~i; --i) {
		assert(dp[i + 1][x][y][z]);
		if (s[i] == 'N') {
			x--;
		} else if (s[i] == 'A') {
			y -= x;
		} else if (s[i] == 'C') {
			z -= y;
		} else if (s[i] == '?') {
			if (x >= 1 && dp[i][x - 1][y][z]) {
				ans[i] = 'N', x--;
			} else if (y >= x && dp[i][x][y - x][z]) {
				ans[i] = 'A', y -= x;
			} else if (z >= y && dp[i][x][y][z - y]) {
				ans[i] = 'C', z -= y;
			} else {
				ans[i] = 'B';
			}
		}
	}
	assert(x == 0 && y == 0 && z == 0);
	cout << ans << '\n';
}