#include<bits/stdc++.h>
using namespace std;

#define int long long
#define F first 
#define S second
#define pb push_back

const int mol=1e9+7;

bool dp[41][41][415][2501];
void solve(){
    int n, kk;
    cin>>n>>kk;
    string a;
    cin>>a;
    int mx=0;
    
    dp[0][0][0][0]=1;
    for(int i=1;i<=n;i++){
        int m=0;
        auto t=a[i-1];
        for(int j=0;j<=i;j++){
            for(int k=0;k<=400;k++){
                for(int l=0;l<=mx+k;l++){
                    if(l>kk) break;
                    // i=40, j=41, k=11, l=0;
                    // if(i==40)
                    // cerr<<i<<" "<<j<<" "<<k<<" "<<l<<"\n";
                    if(t=='?'){
                        dp[i][j][k][l]|=dp[i-1][j][k][l];
                        if(j) dp[i][j][k][l]|=dp[i-1][j-1][k][l];
                        if(k>=j) dp[i][j][k][l]|=dp[i-1][j][k-j][l];
                        if(l>=k) dp[i][j][k][l]|=dp[i-1][j][k][l-k];
                    }
                    else{
                        if(t=='N'&&j) dp[i][j][k][l]|=dp[i-1][j-1][k][l];
                        else if(t=='A'&&k>=j) dp[i][j][k][l]|=dp[i-1][j][k-j][l];
                        else if(t=='C'&&l>=k) dp[i][j][k][l]|=dp[i-1][j][k][l-k];
                        else if(t!='N'&&t!='A'&&t!='C') dp[i][j][k][l]|=dp[i-1][j][k][l];
                    }
                    if(dp[i][j][k][l]) m=max(m, l);
                    // if(i==40) cerr<<i<<"\n";
                    
                }
            }
        }
        mx=m;
    }
    
    int t1, t2, t3, t4=-1;
    for(int j=0;j<=n;j++) for(int k=0;k<=400;k++){
        if(dp[n][j][k][kk]) {t1=n, t2=j, t3=k, t4=kk; break;}
    }
    if(t4==-1){
        cout<<"-1\n";
        return;
    }
    // ????????????????????????????????????????
    string ans=a;
    // cerr<<t1<<" "<<t2<<" "<<t3<<" "<<t4<<"\n";
    for(int i=n-1;i>=0;i--){
        if(a[i]!='?'){
            ans[i]=a[i];
            if(a[i]=='N') t1=i, t2=t2-1, t3=t3, t4=t4;
            else if(a[i]=='A') t1=i, t2=t2, t3=t3-t2, t4=t4;
            else if(a[i]=='C') t1=i, t2=t2, t3=t3, t4=t4-t3;
            else t1=i, t2=t2, t3=t3, t4=t4;
        }
        else{
            if(dp[i][t2][t3][t4]) t1=i, t2=t2, t3=t3, t4=t4, ans[i]='Z';
            else if(t2&&dp[i][t2-1][t3][t4]) t1=i, t2=t2-1, t3=t3, t4=t4, ans[i]='N';
            else if(t3>=t2&&dp[i][t2][t3-t2][t4]) t1=i, t2=t2, t3=t3-t2, t4=t4, ans[i]='A';
            else if(t4>=t3&&dp[i][t2][t3][t4-t3]) t1=i, t2=t2, t3=t3, t4=t4-t3, ans[i]='C';
        }
    }
    cout<<ans<<"\n";
}

signed main(){
    ios::sync_with_stdio(0);cin.tie(0);
    // int t;
    // cin>>t;
    // while(t--)
    solve();
    return 0;
}