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

using ll = long long;
//#define int ll
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
using pii = pair<int, int>;
using vi = vector<int>;
#define fi first
#define se second
#define pb push_back

const int I=40,J=40*(40-1)/2,K=2500;

using cube=array<array<bitset<K+1>,J+1>,I+1>;

void set_i(cube&old,cube&now) {
    for (int i = 0; i <= I; i++)
        if (i - 1 >= 0)
            for (int j = 0; j <= J; j++)
                now[i][j] |= old[i - 1][j];
}

void set_j(cube&old,cube&now) {
    for (int i = 0; i <= I; i++)
        for (int j = 0; j <= J; j++)
            if (j - i >= 0)
                now[i][j] |= old[i][j - i];
}

void set_k(cube&old,cube&now) {
    for (int i = 0; i <= I; i++)
        for (int j = 0; j <= J; j++)
            now[i][j] |= old[i][j] << j;
}

pii find_any(cube&where,int k)
{
    for (int i = 0; i <= I; i++)
        for (int j = 0; j <= J; j++)
            if(where[i][j][k])
                return {i,j};
    cout<<-1,exit(0);
}

cube dp[I+1];

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    int n,k;
    cin>>n>>k;
    string s;
    cin>>s;
    s="_"+s;
    dp[0][0][0][0]=true;
    for(int pos=1;pos<=n;pos++) {
        if (s[pos] == 'N') {
            set_i(dp[pos-1],dp[pos]);
        }
        else if(s[pos]=='A') {
            set_j(dp[pos-1],dp[pos]);
        }
        else if(s[pos]=='C') {
            set_k(dp[pos-1],dp[pos]);
        }
        else if(s[pos]=='?')
        {
            dp[pos]=dp[pos-1];
            set_i(dp[pos-1],dp[pos]);
            set_j(dp[pos-1],dp[pos]);
            set_k(dp[pos-1],dp[pos]);
        }
        else
            dp[pos]=dp[pos-1];
    }
    auto[i,j]=find_any(dp[n],k);
    for(int pos=n;pos>=1;pos--)
    {
        if(s[pos]=='N')
            i--;
        else if(s[pos]=='A')
            j-=i;
        else if(s[pos]=='C')
            k-=j;
        else if(s[pos]=='?')
        {
#define check(ii,jj,kk,ch) if(ii>=0&&jj>=0&&kk>=0&&dp[pos-1][ii][jj][kk]) s[pos]=ch,tie(i,j,k)=tuple(ii,jj,kk)
            check(i,j,k,'X'); else check(i-1,j,k,'N'); else check(i,j-i,k,'A'); else check(i,j,k-j,'C'); else assert(0);
        }
    }
    cout<<s.substr(1);
}