#ifndef ONLINE_JUDGE
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#include <cassert>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint = modint998244353;
//using mint = modint1000000007;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repu(i, s, t) for (int i = (int)(s); i < (int)(t); i++)
#define repd(i, s, t) for (int i = (int)(s)-1; i >= (int)(t); i--)
#define all(v) v.begin(), v.end()
void _u() { cerr << endl; } template <class H, class... T> void _u(H&& h, T&&... t) { cerr << h << ", "; _u(move(t)...); }
#define U(...) { cerr << #__VA_ARGS__ << ": "; _u(__VA_ARGS__); }
template<typename T> bool chmax(T &a, const T b) { if(a >= b) return false; a = b; return true; }
template<typename T> bool chmin(T &a, const T b) { if(a <= b) return false; a = b; return true; }
template<typename T> istream& operator>>(istream &in, vector<T> &a) { for(T &x: a) in >> x; return in; }
template<typename T> ostream& operator<<(ostream &out, const vector<T> &a) { for(const T &x: a) out << x << ' '; return out; }
const int di[] = {1, 0, -1, 0, 1, 1, -1, -1, 0};
const int dj[] = {0, 1, 0, -1, -1, 1, 1, -1, 0};


template<typename T = int>
struct CC {
    bool initialized;
    vector<T> xs;
    CC(): initialized(false) {}
    void add(T x) { xs.push_back(x); }
    void init() {
        sort(xs.begin(), xs.end());
        xs.erase(unique(xs.begin(), xs.end()), xs.end());
        initialized = true;
    }
    int operator()(T x) {
        if(!initialized) init();
        return lower_bound(xs.begin(), xs.end(), x) - xs.begin();
    }
    T operator[](int i) {
        if(!initialized) init();
        return xs[i];
    }
    int size() {
        if(!initialized) init();
        return xs.size();
    }
};

using S = ll;
S op(S l, S r) { return max(l, r); }
S e() { return 0; }

int main() {
    int n, k;
    cin >> n >> k;
    vector<ll> t(n), x(n), c(n);
    cin >> t >> x >> c;
    rep(i, n) t[i] *= k;

    vector<tuple<ll, ll, int>> items;
    rep(i, n) items.emplace_back(t[i]+x[i], t[i]-x[i], c[i]);
    sort(items.rbegin(), items.rend());

    CC id;
    id.add(0);
    for(auto[px, py, s]: items) id.add(py);
    segtree<S, op, e> st(id.size());
    for(auto[px, py, s]: items) {
        int p = id(py);
        st.set(p, st.prod(p, id.size()) + s);
    }
    ll ans = st.prod(id(0), id.size());
    cout << ans << endl;
    return 0;
}