// Problem:  Not Another Constructive!
// Contest: Virtual Judge - QOJ
// URL: https://vjudge.net/problem/QOJ-8776
// Memory Limit: 2028 MB
// Time Limit: 1000 ms
// Date: 2024-07-25 16:05:22
// 
// Powered by CP Editor (https://cpeditor.org)

/*

*/
#include <bits/stdc++.h>
using namespace std;
inline long long read(){
    long long x=0,w=0;char c=0;
    while(!isdigit(c)) {w|=c=='-';c=getchar();}
    while(isdigit(c)) x=(x<<3)+(x<<1)+(c^48),c=getchar();
    return w?-x:x;
}
int n,k;
char s[100];
bitset<2550> dp[50][50][50];
void dfs(int i,int x,int y,int k){
	if(i==0){
		return;
	}
	if((s[i]=='C'||s[i]=='?')&&dp[i-1][x][y+1][k]){
		s[i]='C';
		dfs(i-1,x,y+1,k);
	}
	else if((s[i]=='A'||s[i]=='?')&&k>=x*y&&dp[i-1][x][y][k-x*y]){
		s[i]='A';
		dfs(i-1,x,y,k-x*y);
	}
	else if((s[i]=='N'||s[i]=='?')&&x>=1&&dp[i-1][x-1][y][k]){
		s[i]='N';
		dfs(i-1,x-1,y,k);
	}
	else if(s[i]=='?'){
		s[i]='O';
		dfs(i-1,x,y,k);
	}
	else{
		dfs(i-1,x,y,k);
	}
}
int main(){ 
	scanf("%d%d%s",&n,&k,s+1);
	for(int i=0;i<=n;i++){
		dp[0][0][i][0]=1;
	}
	for(int i=1;i<=n;i++){
		for(int j=0;j<=n;j++){
			for(int l=0;l<=n;l++){
				if(l>=1&&(s[i]=='C'||s[i]=='?')){
					dp[i][j][l-1]=dp[i][j][l-1]|dp[i-1][j][l];
				}
				if(s[i]=='A'||s[i]=='?'){
					dp[i][j][l]=dp[i][j][l]|(dp[i-1][j][l]<<(j*l));
				}
				if(j<i&&(s[i]=='N'||s[i]=='?')){
					dp[i][j+1][l]=dp[i][j+1][l]|dp[i-1][j][l];
				}
				if(s[i]=='?'||(s[i]!='A'&&s[i]!='C'&&s[i]!='N')){
					dp[i][j][l]=dp[i][j][l]|dp[i-1][j][l];
				}
			}
		}
	}
	bool flag=0;
	for(int i=0;i<=n;i++){
		if(dp[n][i][0][k]){
			flag=1;
			dfs(n,i,0,k);
			break;
		}
	}
	if(flag){
		printf("%s",s+1);
		return 0;
	}
	printf("-1");
	return 0; 
}
/*

*/