#include<bits/stdc++.h>
using namespace std;
const int N=45;
const int M=2505;
int n,m,c1,c2;
char s[N];
bitset<M> f[N][N][N];//前$i$个位置[1,i]有$j$个$N$[i+1,n]有$k$个$C$的方案
char ans[N];
signed main(){
    scanf("%d%d",&n,&m);
    scanf("%s",s+1);
    for(int i=1;i<=n;i++){
        if(s[i]=='C'||s[i]=='?')c2++;
        if(s[i]=='C')c1++;
    }
    for(int i=c1;i<=c2;i++)f[0][0][i][0]=1;
    for(int i=1;i<=n;i++){
        for(int j=0;j<=i;j++){
            for(int k=0;k<=n-i;k++){
                if((s[i]=='N'&&j)||(s[i]=='?'&&j)){
                    f[i][j][k]|=f[i-1][j-1][k];
                }
                if(s[i]=='C'||(s[i]=='?')){
                    f[i][j][k]|=f[i-1][j][k+1];
                }
                if((s[i]=='A'&&j*k<=M)||(s[i]=='?'&&j*k<=M)){
                    f[i][j][k]|=f[i-1][j][k]<<(j*k);
                }
                if(s[i]!='A'&&s[i]!='N'&&s[i]!='C'){
                    f[i][j][k]|=f[i-1][j][k];
                }
            }
        }
    }
    for(int num=0;num<=n;num++){
        if(!(int)f[n][num][0][m])continue;
        for(int i=n,j=num,k=0,cnt=m;i;i--){
            if(s[i]=='N'||(s[i]=='?'&&j&&f[i-1][j-1][k][cnt])){
                ans[i]='N';
                j--;
            }else if(s[i]=='C'||(s[i]=='?'&&f[i-1][j][k+1][cnt])){
                ans[i]='C';
                k++;
            }else if(s[i]=='A'||(s[i]=='?'&&cnt>=j*k&&f[i-1][j][k][cnt-j*k])){
                ans[i]='A';
                cnt-=j*k;
            }else if(s[i]=='?')ans[i]='O';
            else ans[i]=s[i];
        }
        for(int i=1;i<=n;i++)cout<<ans[i];
        cout<<endl;
        return 0;
    }
    puts("-1");
    return 0;
}