#include<iostream>
#include<cstring>
#include<algorithm>
#include<bitset>
using namespace std;
int read(){
	int ret=0,f=1;char c=getchar();
	while(c>57||c<48){if(c=='-')f= -1;c=getchar();}
	while(c<=57&&c>=48)ret=(ret<<3)+(ret<<1)+(c-48),c=getchar();
	return ret*f;
}
void write(int x){
	if(x<0) x= -x,putchar('-');
	if(x>9)write(x/10);
	putchar(x%10+48);
}
const int maxn=42;
const int maxk=2505;
const int mod =1e9+7;
int n,m;
bitset<maxk>f[maxn][maxn][maxn];
char str[maxn],ans[maxn];
void solve(){
    n=read(),m=read();
    cin>>str+1;
    for(int i=0;i<=n;i++)f[1][0][i][0]=1;
    for(int i=1;i<=n;i++){
        for(int j=0;j<=n;j++){
            for(int k=0;k<=n;k++){
                if(str[i]=='N'||str[i]=='?')f[i+1][j+1][k]|=f[i][j][k];
                if(str[i]=='A'||str[i]=='?')f[i+1][j][k]|=f[i][j][k]<<(j*k);
                if(str[i]=='C'||str[i]=='?')if(k)f[i+1][j][k-1]|=f[i][j][k];
                if(str[i]!='N'&&str[i]!='A'&&str[i]!='C')f[i+1][j][k]|=f[i][j][k];
            }
        }
    }
    for(int j=0;j<=n;j++){
        if(!f[n+1][j][0][m])continue;
        for(int i=n,k=0,t=m;i;i--){
            bool fg=1;
            if(fg&&(str[i]=='N'||str[i]=='?'))if(j>=1&&f[i][j-1][k][t])j--,ans[i]='N',fg=0;
            if(fg&&(str[i]=='A'||str[i]=='?'))if(t>=j*k&&f[i][j][k][t-j*k])t-=j*k,ans[i]='A',fg=0;
            if(fg&&(str[i]=='C'||str[i]=='?'))if(f[i][j][k+1][t])k++,ans[i]='C',fg=0;
            if(fg&&str[i]=='?')ans[i]='B',fg=0;
            if(fg)ans[i]=str[i];
        }
        cout<<ans+1;
        exit(0);
    }
    puts("-1");
}
signed main(){
    int T=1;
    while(T--)solve();
    return 0;
}