#include<bits/stdc++.h>
using namespace std;
const int N=45;
const int inf=1e9+7;

static char buf[1000000],*p1=buf,*p2=buf;
#define getchar() p1==p2&&(p2=(p1=buf)+fread(buf,1,1000000,stdin),p1==p2)?EOF:*p1++
inline int wrd(){int x=0,f=1;char c=getchar();while(c<'0' || c>'9'){if(c=='-') f=-1;c=getchar();}while(c>='0' && c<='9') {x=(x<<3)+(x<<1)+c-48;c=getchar();}return x*f;}

int n,m,tn,tc,ta;
bool f[N][N][N][2505];
char g[N][N][N][2505];
string a;

void write(int p,int i,int j,int k){
	if(!p) return;
	char o=g[p][i][j][k];
	if(o=='N') write(p-1,i-1,j,k);
	else if(o=='C') write(p-1,i,j+1,k);
	else if(o=='A') write(p-1,i,j,k-i*j);
	else write(p-1,i,j,k);
	putchar(o);
}

signed main(){
	cin >> n >> m >> a,a=" "+a;
	for(int i=1;i<=n;++i) tn+=(a[i]=='N'),tc+=(a[i]=='C'),ta+=(a[i]=='A');
	for(int i=tc;i<=n-tn-ta;++i) f[0][0][i][0]=1;
	for(int p=0;p<n;++p){
		for(int i=0;i<=p;++i){
			for(int j=0;j<=n-p;++j){
				for(int k=0;k<=m;++k){
					if(!f[p][i][j][k]) continue;
					if(a[p+1]=='N'||a[p+1]=='?'){
						f[p+1][i+1][j][k]=1,g[p+1][i+1][j][k]='N';
					}
					if(a[p+1]=='C'||a[p+1]=='?'){
						f[p+1][i][j-1][k]=1,g[p+1][i][j-1][k]='C';
					}
					if(a[p+1]=='A'||a[p+1]=='?'){
						if(k+i*j<=m) f[p+1][i][j][k+i*j]=1,g[p+1][i][j][k+i*j]='A';
					}
					if(a[p+1]=='?') f[p+1][i][j][k]=1,g[p+1][i][j][k]='B';
					if(a[p+1]!='N'&&a[p+1]!='C'&&a[p+1]!='A'&&a[p+1]!='?')
						f[p+1][i][j][k]=1,g[p+1][i][j][k]=a[p+1];
				}
			}
		}
	}
	for(int i=tn;i<=n-tc-ta;++i)
		if(f[n][i][0][m]) write(n,i,0,m),exit(0);
	puts("-1");
}