#pragma GCC optimize(2)
#pragma GCC optimize(3)

#include <bits/stdc++.h>

using namespace std;

using i64 = long long;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int n, k;
	cin >> n >> k;
	
	string s;
	cin >> s;
	
	auto dfs = [&](auto &self, int p, int N, int NA, int NAC, string t) -> void {
		if (NAC > k) {
			return;
		}
		
		int q = N + n - p;
		q /= 3;
		q++;
		if (NAC + NA * q + N * q * q + q * q * q < k) {
			return;
		}
		
		if (p == n) {
			if (NAC == k) {
				cout << t << "\n";
				exit(0);
			}
			return;
		}
		
		if (s[p] == '?') {
			self(self, p + 1, N + 1, NA, NAC, t + "N");
			self(self, p + 1, N, NA + N, NAC, t + "A");
			self(self, p + 1, N, NA, NAC + NA, t + "C");
			self(self, p + 1, N, NA, NAC, t + "Q");
		} else if (s[p] == 'N') {
			self(self, p + 1, N + 1, NA, NAC, t + s[p]);
		} else if (s[p] == 'A') {
			self(self, p + 1, N, NA + N, NAC, t + s[p]);
		} else if (s[p] == 'C') {
			self(self, p + 1, N, NA, NAC + NA, t + s[p]);
		} else {
			self(self, p + 1, N, NA, NAC, t + s[p]);
		}
	};
	
	dfs(dfs, 0, 0, 0, 0, "");
	
	cout << -1 << "\n";
	
	return 0;
}