#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define mp make_pair
#define si(x) int(x.size())
const int mod=998244353,MAX=2503,INF=15<<26;

bitset<MAX> dp[41][41][401];

int main(){
    
    std::ifstream in("text.txt");
    std::cin.rdbuf(in.rdbuf());
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    int N,K;cin>>N>>K;
    string S;cin>>S;
    dp[0][0][0][0]=true;
    
    for(int i=0;i<N;i++){
        for(int j=0;j<=i;j++){
            for(int k=0;k<=((i+1)/2)*(i/2);k++){
                if(S[i]=='?'){
                    dp[i+1][j+1][k]|=dp[i][j][k];
                    dp[i+1][j][k+j]|=dp[i][j][k];
                    dp[i+1][j][k]|=dp[i][j][k]<<k;
                    dp[i+1][j][k]|=dp[i][j][k];
                }else if(S[i]=='N'){
                    dp[i+1][j+1][k]|=dp[i][j][k];
                }else if(S[i]=='A'){
                    dp[i+1][j][k+j]|=dp[i][j][k];
                }else if(S[i]=='C'){
                    dp[i+1][j][k]|=dp[i][j][k]<<k;
                }else{
                    dp[i+1][j][k]|=dp[i][j][k];
                }
            }
        }
    }
    
    string ans;
    
    for(int jj=0;jj<=N;jj++){
        for(int kk=0;kk<=400;kk++){
            if(dp[N][jj][kk][K]){
                int i=N,j=jj,k=kk,x=K;
                while(i){
                    i--;
                    if(S[i]=='?'){
                        if(j-1>=0&&dp[i][j-1][k][x]){
                            j--;
                            ans+='N';
                        }else if(k-j>=0&&dp[i][j][k-j][x]){
                            k-=j;
                            ans+='A';
                        }else if(x-k>=0&&dp[i][j][k][x-k]){
                            x-=k;
                            ans+='C';
                        }else{
                            assert(dp[i][j][k][x]);
                            ans+='Z';
                        }
                    }else if(S[i]=='N'){
                        j--;
                        ans+=S[i];
                    }else if(S[i]=='A'){
                        k-=j;
                        ans+=S[i];
                    }else if(S[i]=='C'){
                        x-=k;
                        ans+=S[i];
                    }else{
                        ans+=S[i];
                    }
                }
                
                reverse(all(ans));
                
                cout<<ans<<endl;
                
                return 0;
            }
        }
    }
    
    cout<<-1<<endl;
}