#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;

const int N=110;

int n, k, a[N], x[N], sum, state;
map<int, int> dp, check;
vector<pair<int, int> > v; //za nove sume, prvo prolazim kroz mapu pa tek onda njih dodajem da ne pokvarim it!=dp.end

int main()
{
    scanf ("%d%d", &n, &k);
    for (int i=1;i<=n;i++) scanf ("%d", &a[i]);
    for (int i=1;i<=n;i++)
    {
        scanf ("%d", &x[i]);
        x[i]*=-k;
        x[i]+=a[i];
    }

    for (int i=1;i<=n;i++)
    {
        v.clear();
        for (map<int, int>::iterator it=dp.begin();it!=dp.end();it++)
        {
            sum=it->f;
            state=it->s;
            if (check[sum+x[i]]) dp[sum+x[i]]=max(dp[sum+x[i]], state+a[i]);
            else v.push_back(make_pair(sum+x[i], state+a[i]));
        }
        for (int j=0;j<v.size();j++)
        {
            check[v[j].f]=true;
            dp[v[j].f]=max(dp[v[j].f], v[j].s);
        }
        dp[x[i]]=max(dp[x[i]], a[i]);
        check[x[i]]=true;
    }

    if (check[0]) printf ("%d", dp[0]);
    else printf ("-1");

    return 0;
}