// #pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
// #include <x86intrin.h>
using namespace std;
#if __cplusplus >= 202002L
using namespace numbers;
#endif

int main(){
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(ios::badbit | ios::failbit);
	int n, obj;
	string s;
	cin >> n >> obj >> s;
	array<int, 2> th{n, (n >> 1) * (n + 1 >> 1)};
	#ifdef LOCAL
	const int mx = 2;
	#else
	const int mx = 2'500;
	#endif
	vector dp(n + 1, vector(th[0] + 1, vector<bitset<mx + 1>>(th[1] + 1)));
	dp[0][0][0][0] = 1;
	for(auto i = 0; i < n; ++ i){
		if(s[i] == '?' || s[i] == 'N'){
			for(auto j = 0; j < th[0]; ++ j){
				for(auto k = 0; k <= th[1]; ++ k){
					dp[i + 1][j + 1][k] |= dp[i][j][k];
				}
			}
		}
		if(s[i] == '?' || s[i] == 'A'){
			for(auto j = 0; j <= th[0]; ++ j){
				for(auto k = 0; k + j <= th[1]; ++ k){
					dp[i + 1][j][k + j] |= dp[i][j][k];
				}
			}
		}
		if(s[i] == '?' || s[i] == 'C'){
			for(auto j = 0; j <= th[0]; ++ j){
				for(auto k = 0; k <= th[1]; ++ k){
					dp[i + 1][j][k] |= dp[i][j][k] << k;
				}
			}
		}
		if(s[i] == '?' || ranges::count("NAC", s[i]) == 0){
			for(auto j = 0; j <= th[0]; ++ j){
				for(auto k = 0; k <= th[1]; ++ k){
					dp[i + 1][j][k] |= dp[i][j][k];
				}
			}
		}
	}
	for(auto cj = 0; cj <= th[0]; ++ cj){
		for(auto ck = 0; ck <= th[1]; ++ ck){
			if(dp[n][cj][ck][obj]){
				for(auto i = n - 1; i >= 0; -- i){
					if(s[i] == '?' || s[i] == 'N'){
						if(cj > 0 && dp[i][cj - 1][ck][obj]){
							s[i] = 'N';
							-- cj;
							goto DONE;
						}
					}
					if(s[i] == '?' || s[i] == 'A'){
						if(cj <= ck && dp[i][cj][ck - cj][obj]){
							s[i] = 'A';
							ck -= cj;
							goto DONE;
						}
					}
					if(s[i] == '?' || s[i] == 'C'){
						if(obj >= ck && dp[i][cj][ck][obj - ck]){
							s[i] = 'C';
							obj -= ck;
							goto DONE;
						}
					}
					if(s[i] == '?' || ranges::count("NAC", s[i]) == 0){
						if(dp[i][cj][ck][obj]){
							s[i] = s[i] == '?' ? 'Z' : s[i];
							goto DONE;
						}
					}
					DONE:;
				}
				cout << s << "\n";
				return 0;
			}
		}
	}
	cout << "-1\n";
	return 0;
}

/*

*/