#include <bits/stdc++.h>
using namespace std;

template <class T> using V = vector<T>;
template <class T> using VV = V<V<T>>;

const int MAXK = 2510;
using Bitset = bitset<MAXK>;
const int MAXL = 42;
const int MAXN = 42;
const int MAXNA = 410;
Bitset dp[MAXL][MAXN][MAXNA];

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

	int L, K;
	cin >> L >> K;
	string S;
	cin >> S;
	assert(L == int(S.size()));

	dp[0][0][0].set(0);

	for (int i = 0; i < L; i++) {
		int c = S[i];

		// Append N
		if (c == '?' || c == 'N') {
			for (int n = 0; n+1 < MAXN; n++) {
				for (int na = 0; na < MAXNA; na++) {
					dp[i+1][n+1][na] |= dp[i][n][na];
				}
			}
		}

		// Append A
		if (c == '?' || c == 'A') {
			for (int n = 0; n < MAXN; n++) {
				for (int na = 0; na+n < MAXNA; na++) {
					dp[i+1][n][na+n] |= dp[i][n][na];
				}
			}
		}

		// Append C
		if (c == '?' || c == 'C') {
			for (int n = 0; n < MAXN; n++) {
				for (int na = 0; na < MAXNA; na++) {
					dp[i+1][n][na] |= (dp[i][n][na] << na);
				}
			}
		}

		// Append non-NAC
		if (c == '?' || (c != 'N' && c != 'A' && c != 'C')) {
			for (int n = 0; n < MAXN; n++) {
				for (int na = 0; na < MAXNA; na++) {
					dp[i+1][n][na] |= dp[i][n][na];
				}
			}
		}
	}

	using State = array<int, 3>;
	auto state = State{-1,-1,-1};
	for (int n = 0; n < MAXN; n++) {
		for (int na = 0; na < MAXNA; na++) {
			if (dp[L][n][na].test(K)) {
				state = {n, na, K};
			}
		}
	}

	if (state[0] != -1) {
		string res;
		// (N, NA, NAC)
		for (int i = L-1; i >= 0; i--) {
			auto& [n, na, nac] = state;
			char c = S[i];

			// N
			if ((c == '?' || c == 'N') && n-1 >= 0 && dp[i][n-1][na][nac]) {
				n -= 1;
				res += 'N';
				continue;
			}

			// A
			if ((c == '?' || c == 'A') && na-n >= 0 && dp[i][n][na-n][nac]) {
				na -= n;
				res += 'A';
				continue;
			}

			// C
			if ((c == '?' || c == 'C') && nac-na >= 0 && dp[i][n][na][nac-na]) {
				nac -= na;
				res += 'C';
				continue;
			}

			// Non-NAC
			assert(c == '?' || (c != 'N' && c != 'A' && c != 'C'));
			assert(dp[i][n][na][nac]);
			res += (c == '?' ? 'X' : c);
		}
		assert(state[0] == 0 && state[1] == 0 && state[2] == 0);
		reverse(begin(res), end(res));

		cout << res << '\n';
	} else {
		cout << -1 << '\n';
	}

	return 0;
}