#include<iostream>
#include<bitset>
using namespace std;
const int N=55;
int n,k;
char s[N],ans[N];
bitset<3005>f[N][N][N];
void print(int i,int a,int b,int sum){
	if(i==0) return;
	if(s[i]!='N'&&s[i]!='A'&&s[i]!='C'&&f[i-1][a][b][sum]){
		if(s[i]=='?')ans[i]='B';
		else ans[i]=s[i];
		print(i-1,a,b,sum);	
	}
	else if(a-1>=0&&(s[i]=='N'||s[i]=='?')&&f[i-1][a-1][b][sum]){
		ans[i]='N';
		print(i-1,a-1,b,sum);
	}
	else if(sum-a*b>=0&&(s[i]=='A'||s[i]=='?')&&f[i-1][a][b][sum-a*b]){
		ans[i]='A';
		print(i-1,a,b,sum-a*b);
	}
	else if((s[i]=='C'||s[i]=='?')&&f[i-1][a][b+1][sum]){
		ans[i]='C';
		print(i-1,a,b+1,sum);
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin>>n>>k>>s+1;
	for(int i=0;i<=n;i++) f[0][0][i][0]=1;
	for(int i=1;i<=n;i++){
		for(int a=0;a<=i;a++){
			for(int b=0;b<=n-i;b++){
				if(s[i]=='?'||s[i]=='N') f[i][a+1][b]|=f[i-1][a][b];
				if(s[i]=='?'||s[i]=='A') f[i][a][b]|=(f[i-1][a][b]<<(a*b));
				if(s[i]=='?'||s[i]=='C') f[i][a][b]|=f[i-1][a][b+1];
				if(s[i]!='N'&&s[i]!='A'&&s[i]!='C') f[i][a][b]|=f[i-1][a][b];
			}
		}
	}
	for(int i=0;i<=n;i++){
		if(f[n][i][0][k]){
			print(n,i,0,k);
			for(int j=1;j<=n;j++) cout<<ans[j];
			return 0;
		}
	}
	cout<<-1<<'\n';
	return 0;
}