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

const int N=110;

int a[N], b[N], n, k, sum, state;
map<int, int> dp;
vector<pair<int, int> > v;

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", &b[i]), b[i]*=k;

    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 (dp[sum+a[i]-b[i]]==0) v.push_back(make_pair(sum+a[i]-b[i], state+a[i]));
            else dp[sum+a[i]-b[i]]=max(dp[sum+a[i]-b[i]], state+a[i]);
        }
        for (int j=0;j<v.size();j++) dp[v[j].f]=max(dp[v[j].f], v[j].s);
        dp[a[i]-b[i]]=max(dp[a[i]-b[i]], a[i]);
    }

    printf ("%d", dp[0]);

    return 0;
}