#include <bits/stdc++.h>

using namespace std;

#define iter(v) v.begin(), v.end()
#define SZ(v) int(v.size())
#define pb emplace_back
#define ff first
#define ss second

using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

#ifdef zisk
void debug(){cerr << "\n";}
template<class T, class ... U>
void debug(T a, U ... b){ cerr << a << " ", debug(b...); }
template<class T> void pary(T l, T r){
	while(l != r) cerr << *l << " ", l++;
	cerr << "\n";
}
#else
#define debug(...) void()
#define pary(...) void()
#endif

template<class A, class B>
ostream& operator<<(ostream& o, pair<A, B> p){
	return o << '(' << p.ff << ',' << p.ss << ')';
}

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

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(0);

	int n, K;
	cin >> n >> K;

	string s;
	cin >> s;
	s = " " + s;
	dp[0][0][0][0] = 1;
	auto bad = [&](char c){
		return c != 'N' && c != 'A' && c != 'C';
	};
	
	for(int i = 0; i < n; i++){
		char c = s[i + 1];
		for(int N = 0; N <= 40; N++){
			for(int NA = 0; NA <= 400; NA++){
				if(bad(c)) dp[i + 1][N][NA] |= dp[i][N][NA];
				if(c == 'N' || c == '?'){
					if(N + 1 <= 40) dp[i + 1][N + 1][NA] |= dp[i][N][NA];
				}
				if(c == 'A' || c == '?'){
					if(NA + N <= 400) dp[i + 1][N][NA + N] |= dp[i][N][NA];
				}
				if(c == 'C' || c == '?'){
					dp[i + 1][N][NA] |= dp[i][N][NA] << NA;
				}
			}
		}
	}
	
	int N = -1, NA = -1, NAC = -1;
	for(N = 0; N <= 40; N++){
		for(NA = 0; NA <= 400; NA++){
			if(dp[n][N][NA][K]){
				NAC = K;
				break;
			}
		}
		if(NAC != -1) break;
	}
	if(NAC == -1){
		cout << "-1\n";
		return 0;
	}

	int i;
	auto try_N = [&](){
		if(N - 1 < 0 || !dp[i - 1][N - 1][NA][NAC]) return false;
		//debug("try_N ok", i);
		N--;
		return true;
	};
	auto try_A = [&](){
		if(NA - N < 0 || !dp[i - 1][N][NA - N][NAC]) return false;
		//debug("try_A ok", i);
		NA -= N;
		return true;
	};
	auto try_C = [&](){
		if(NAC - NA < 0 || !dp[i - 1][N][NA][NAC - NA]) return false;
		//debug("try_C ok", i);
		NAC -= NA;
		return true;
	};

	string ans(n, ' ');
	for(i = n; i >= 1; i--){
		char c = s[i];
		//debug("start", i, ":", N, NA, NAC, dp[i][N][NA][NAC]);
		if((c == 'N' || c == '?') && try_N()) ans[i - 1] = 'N';
		else if((c == 'A' || c == '?') && try_A()) ans[i - 1] = 'A';
		else if((c == 'C' || c == '?') && try_C()) ans[i - 1] = 'C';
		else if(bad(c)) ans[i - 1] = s[i] == '?' ? 'O' : s[i];
		else assert(false);
		//debug("OK", i, c, ans[i - 1]);
	}
	cout << ans << "\n";

}