#include<bits/stdc++.h>
#define mod 998244353
#define vec vector
#define X first
#define Y second
#define Qu queue
#define St stack
#define Bi bitset
#define gtt getchar
#define grt greater
#define p_b push_back
#define m_p make_pair
#define int long long
#define ptt(x) putchar(x)
#define pii pair<int,int>
#define Pq priority_queue
#define mem(a,x) memset(a,x,sizeof a)
#define mep(a,b) memcpy(a,b,sizeof a)
#define fz(i,a,b) for(int i=a;i<=b;i++)
#define fd(i,b,a) for(int i=b;i>=a;i--)
#define eg(i,u) for(auto i:e[u])
using namespace std;
template<typename T>void rd(T &x){
    x=0;
    int f=1;
    char ch=gtt();
    for(;ch<'0'||ch>'9';ch=gtt()) if(ch=='-') f=-1;
    for(;ch>='0'&&ch<='9';ch=gtt()) x=(x<<1)+(x<<3)+(ch^48);
    x*=f;
}
void wr(char s){putchar(s);}
template<typename T>void wr(T x){
    if(x<0) ptt('-'),x=-x;
    if(x>9) wr(x/10);
    ptt(x%10+'0');
}
template<typename T,typename ...Args>void rd(T &x,Args &...args){rd(x);rd(args...);}
template<typename T,typename ...Args>void wr(T x,Args ...args){wr(x);wr(args...);}
int n,K;
char s[55],ans[55];
Bi<2505> f[55][55][55];
signed main(){
    rd(n,K);
    scanf("%s",s+1);
    fz(i,0,n) f[0][0][i][0]=1;
    fz(i,1,n)
        fz(j,0,i)
            fz(k,0,n-i){
                if((s[i]=='N'||s[i]=='?')&&j) f[i][j][k]|=f[i-1][j-1][k];
                if(s[i]=='C'||s[i]=='?') f[i][j][k]|=f[i-1][j][k+1];
                if(s[i]=='A'||s[i]=='?') f[i][j][k]|=f[i-1][j][k]<<(j*k);
                if(s[i]!='N'&&s[i]!='A'&&s[i]!='C') f[i][j][k]|=f[i-1][j][k];
            }
    int flag=-1;
    fz(i,0,n)
        if(f[n][i][0][K]) flag=i;
    if(flag==-1) wr(flag),exit(0);
    int j=flag,k=0,now=K;
    fd(i,n,1){
        if(s[i]=='N'||(s[i]=='?'&&j&&f[i-1][j-1][k][now])) ans[i]='N',j--;
        else if(s[i]=='C'||(s[i]=='?'&&f[i-1][j][k+1][now])) ans[i]='C',k++;
        else if(s[i]=='A'||(s[i]=='?'&&now>=j*k&&f[i-1][j][k][now-j*k])) ans[i]='A',now-=j*k;
        else ans[i]=s[i];
    }
    fz(i,1,n) printf("%c",ans[i]);
    return 0;
}