#include<bits/stdc++.h>
using namespace std;
bitset<2501> f[41][41][41];
int cntn,N,K;
string S;
char SS[505050];
int main(){
	cin>>N>>K>>S;
	S=" "+S;
	for(int i=0;i<=N;i++)f[0][0][i][0]=1;
	for(int i=0;i<N;i++){
		for(int n=0;n<=N;n++){
			for(int c=0;c<=N-i;c++){
					if(n+1<=N&&(S[i+1]=='N'||S[i+1]=='?')){
				    	f[i+1][n+1][c]|=f[i][n][c];	
					}
					if(c>=1&&(S[i+1]=='C'||S[i+1]=='?')){
						f[i+1][n][c-1]|=f[i][n][c]; 
					}
					if(n*c<=K&&(S[i+1]=='A'||S[i+1]=='?')){
						f[i+1][n][c]|=(f[i][n][c]<<(n*c)); 
					}
					if(S[i+1]!='A'&&S[i+1]!='C'&&S[i+1]!='N'){
						f[i+1][n][c]|=f[i][n][c];
					}
			}
		}
	} 
	int pos=-1;
	for(int i=0;i<=N;i++){
		if(f[N][i][0][K]) pos=i;
	} 
	if(pos==-1){
		cout<<-1;
	}else{
		for(int i=N,nn=pos,cc=0,kk=K;i>=1;i--){
			if((S[i]=='N'||S[i]=='?')&&f[i-1][nn-1][cc][kk]){
				SS[i-1]='N';nn--;
			}else{
				if((S[i]=='C'||S[i]=='?')&&f[i-1][nn][cc+1][kk]){
					SS[i-1]='C';cc++;
				}else{
					if((kk>=nn*cc&&S[i]=='A'||S[i]=='?')&&f[i-1][nn][cc][kk-nn*cc]){
						SS[i-1]='A';kk-=nn*cc;
					}else{
						if(S[i]=='?')SS[i-1]='O';
						else SS[i-1]=S[i];
					}
				} 
			} 
		}
		for(int i=0;i<N;i++){
			cout<<SS[i];
		}
		exit(0);
	}
	return 0;
}