#include<bits/stdc++.h>
using namespace std;using ll=long long;
int rd(int x=0,char c=getchar()){int f=1;while(!isdigit(c))f=(c^'-'?1:-1),c=getchar();while(isdigit(c))x=x*10+(c^48),c=getchar();return x*f;}
const int N=42,K=2505;
int n,k;
bitset<K> f[N][N][N];
char s[N];
int main(){
	n=rd(),k=rd();
	scanf("%s",s+1);for(int i=0;i<=n;i++)f[0][0][i][0]=1;
	for(int i=0;i<n;i++)for(int j=0;j<n;j++)for(int c=0;c<=n-i;c++){
		if(s[i+1]=='N'||s[i+1]=='?')f[i+1][j+1][c]|=f[i][j][c];
		if(s[i+1]=='A'||s[i+1]=='?')f[i+1][j][c]|=(f[i][j][c]<<(j*c));
		if(s[i+1]=='C'||s[i+1]=='?')if(c)f[i+1][j][c-1]|=f[i][j][c];
		if(s[i+1]!='N'&&s[i+1]!='A'&&s[i+1]!='C'&&s[i+1]!='?')f[i+1][j][c]|=f[i][j][c];
	}
	int x=0;for(;x<=n;x++)if(f[n][x][0][k])break;
	if(x>n)return puts("-1"),0;
	int c=0;
	for(int i=n;i;i--){
		if(s[i]=='N')x--;
		if(s[i]=='C')c++;
		if(s[i]=='A')k-=c*x;
		if(s[i]=='?'){
			if(x&&f[i-1][x-1][c][k])s[i]='N',x--;
			else if(f[i-1][x][c+1][k])s[i]='C',c++;
			else s[i]='A',k-=c*x;
		} 
	}
	printf("%s",s+1);
	return 0;
}