#include<bits/stdc++.h>
#define ll long long
#define R register
#define isn (s[i]=='N')
#define isa (s[i]=='A')
#define isc (s[i]=='C')
#define isq (s[i]=='?')
using namespace std;
const int N=55,K=2505;
bitset<K> f[N][N][N];
int n,m;char res[N];string s;
int main(){
	ios::sync_with_stdio(0);cin.tie(0),cout.tie(0);
	cin>>n>>m>>s;s=" "+s;
	for(R int i=0;i<=n;++i)f[0][0][i][0]=1;
	for(R int i=1;i<=n;++i){
		for(R int j=0;j<=i;++j){
			for(R int k=0;k<=n-i;++k){
				// cout<<i<<' '<<j<<' '<<k<<' '<<s[i]<<' '<<(isn)<<' '<<(isa)<<' '<<(isc)<<'\n';
				if(!isn&&!isa&&!isc)f[i][j][k]|=f[i-1][j][k];
				if((isn||isq)&&j)f[i][j][k]|=f[i-1][j-1][k];
				if((isc||isq))f[i][j][k]|=f[i-1][j][k+1];
				if((isa||isq))f[i][j][k]|=(f[i-1][j][k]<<(j*k));
			}
		}
	}
	int pos=-1;for(R int i=0;i<=n;++i)if(f[n][i][0][m])pos=i;
	// cout<<f[0][0][0][0]<<' '<<f[1][0][0][0]<<'\n';
	if(pos==-1)return cout<<"-1",0;
	for(R int i=n,j=pos,sumc=0,all=m;i>=1;--i){
		if(isn||(isq&&j&&f[i-1][j-1][sumc][all]))res[i]='N',--j;
		else if(isa||(isq&&j*sumc<=all&&f[i-1][j][sumc][all-j*sumc]))res[i]='A',all-=j*sumc;
		else if(isc||(isq&&f[i-1][j][sumc+1][all]))res[i]='C',++sumc;
		else res[i]=s[i];
	}
	for(R int i=1;i<=n;++i)cout<<res[i];
	return 0;
}