//Man always remember love because of romance only!
#include<bits/stdc++.h>
using namespace std;
inline int read(){
    int n=0,w=0; char ch=0;
    while(!isdigit(ch)) {w|=ch=='-';ch=getchar();}
    while(isdigit(ch)) n=(n<<3)+(n<<1)+(ch^48),ch=getchar();
    return w?-n:n;
}
inline void write(int x){
	if(x<0) putchar('-'),x=-x;
    if(x>9) write(x/10);
    putchar(x%10+'0');
}
char s[51],ans[51];
bitset<2501> dp[51][51][51]; 
int main(){
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
	int n=read(),kk=read();
	cin>>s+1;
	for(int i=0;i<=n;i++) dp[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+1;k++){
				if(s[i]=='N'||s[i]=='?'){
					if(j) dp[i][j][k]|=dp[i-1][j-1][k];
				}
				if(s[i]=='A'||s[i]=='?') dp[i][j][k]|=(dp[i-1][j][k]<<(j*k));
				if(s[i]=='C'||s[i]=='?'){
					if(k<n) dp[i][j][k]|=dp[i-1][j][k+1];
				}
				if((s[i]!='N'&&s[i]!='A'&&s[i]!='C')||s[i]=='?') dp[i][j][k]|=dp[i-1][j][k];
			}
		}
	} 
	for(int i=0;i<=n;i++){
		if(dp[n][i][0][kk]){
			int nown=i,nowc=0,sum=kk;
			for(int j=n;j;j--){
				if((s[j]=='N'||s[j]=='?')&&nown&&dp[j-1][nown-1][nowc][sum]) ans[j]='N',nown--;
				else if((s[j]=='A'||s[j]=='?')&&sum-nown*nowc>=0&&dp[j-1][nown][nowc][sum-nown*nowc]) ans[j]='A',sum-=nown*nowc;
				else if((s[j]=='C'||s[j]=='?')&&nowc<n&&dp[j-1][nown][nowc+1][sum]) ans[j]='C',nowc++;
				else ans[j]=(s[j]=='?')?'B':s[j];
			}
			for(int j=1;j<=n;j++) cout<<ans[j];
			return 0;
		}
	}
	write(-1);
	return 0;
}