#include"bits/stdc++.h"

using lint = int64_t;

using namespace std;

using B = bitset<2502>;
//using B = bitset<10>;

const int N = 42;
const int M = 20*20+5;
B dp[N][N][M];

int main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, cnt;
    string s;
    cin>>n>>cnt>>s;
    dp[0][0][0][0] = true;
    for(int i = 1; i <= n; i++){
        //cout<<i<<"\n";
        char x = s[i-1];
        for(int j = 0; j <= i; j++){ //n
            for(int k = 0; k < M; k++){ //na
                //cout<<j<<" "<<k<<" "<<dp[i-1][j][k]<<"\n";
                if((x == 'N' || x == '?') && j + 1 < N){
                    dp[i][j+1][k] |= dp[i-1][j][k];
                }
                if((x == 'A' || x == '?') && k + j < M){
                    dp[i][j][k+j] |= dp[i-1][j][k];                    
                }
                if((x == 'C' || x == '?')){
                    dp[i][j][k] |= (dp[i-1][j][k] << k);
                }
                if(x != 'N' && x != 'A' && x != 'C'){
                    dp[i][j][k] |= dp[i-1][j][k];
                }
            }
        }
    }
    bool ok = false;
    int targ_j = -1, targ_k = -1;
    for(int j = 0; j < N; j++){ //n
        for(int k = 0; k < M; k++){ //na
            if(dp[n][j][k][cnt]){
                targ_j = j, targ_k = k;
                ok = true;
                break;
            }
        }
    }
    if(!ok){
        cout<<"-1\n";
        return 0;
    }
    int j = targ_j, k = targ_k, goal = cnt;
    string ans = "";
    for(int i = n; i >= 1; i--){
        //cout<<i<<" "<<j<<" "<<k<<" "<<goal<<endl;
        char x = s[i-1];
        if((x == 'N' || x == '?') && j - 1 >= 0 && dp[i-1][j-1][k][goal]){
            ans += 'N';
            j--;
        }
        else if((x == 'A' || x == '?') && k - j >= 0 && dp[i-1][j][k-j][goal]){
            ans += 'A';
            k -= j;                    
        }
        if((x == 'C' || x == '?') && goal - k >= 0 && dp[i-1][j][k][goal - k]){
            ans += 'C';
            goal -= k;
        }
        if((x != 'N' && x != 'A' && x != 'C') && dp[i-1][j][k][goal]){
            ans += (x == '?' ? 'L' : x);
        }
    }
    reverse(ans.begin(), ans.end());
    cout<<ans<<"\n";


    return 0;
}