#include<bits/stdc++.h>
#define p_b push_back
#define m_p make_pair
#define pii pair<int,int>
#define int long long 
using namespace std;
inline int rd(){
	int x=0,f=1; char ch=getchar();
	for(;ch<'0'||ch>'9';ch=getchar())if (ch=='-') f=-1;
	for(;ch>='0'&&ch<='9';ch=getchar())x=(x<<1)+(x<<3)+(ch^48);
	return x*f;
}
const int N=55,INF=0x3f3f3f3f3f3f3f3f;
int n,k;
string s,ans;
bitset<3000> dp[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'&&dp[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]=='?')&&dp[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]=='?')&&dp[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]=='?')&&dp[i-1][a][b+1][sum]){
		ans[i]='C';
		print(i-1,a,b+1,sum);
	}
}

signed main(){
	n=rd(),k=rd();
	cin>>s;s=' '+s;
	for(int i=0;i<=n;i++) dp[0][0][i][0]=1;
	for(int i=1;i<=n;i++){
		for(int a=0;a<=i-1;a++){
			for(int b=0;b<=n-i;b++){
				if(s[i]=='?'||s[i]=='N')dp[i][a+1][b]|=dp[i-1][a][b];
				if(s[i]=='?'||s[i]=='A')dp[i][a][b]|=(dp[i-1][a][b]<<(a*b));
				if(s[i]=='?'||s[i]=='C')dp[i][a][b]|=dp[i-1][a][b+1];
				if(s[i]!='N'&&s[i]!='C'&&s[i]!='A') dp[i][a][b]|=dp[i-1][a][b];
			}
		}
	}
	for(int i=0;i<=n;i++){
		if(dp[n][i][0][k]){
			ans=s;
			print(n,i,0,k);
			for(int j=1;j<=n;j++) cout<<ans[j];
			return 0;
		}
	}
	puts("-1");
	return 0;	
}