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

//* ATCODER
#include<atcoder/all>
using namespace atcoder;
typedef modint998244353 mint;
//*/

/* BOOST MULTIPRECISION
#include<boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
//*/

typedef long long ll;

#define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)

template <typename T> bool chmin(T &a, const T &b) {
	if (a <= b) return false;
	a = b;
	return true;
}

template <typename T> bool chmax(T &a, const T &b) {
	if (a >= b) return false;
	a = b;
	return true;
}

template <typename T> T max(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmax(ret, a[i]);
	return ret;
}

template <typename T> T min(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmin(ret, a[i]);
	return ret;
}

template <typename T> T sum(vector<T> &a){
	T ret = 0;
	for (int i=0; i<(int)a.size(); i++) ret += a[i];
	return ret;
}

ll op(ll a, ll b){
	return max(a, b);
}

ll e(){
	return -1e18;
}


int main(){
	int n; cin >> n;
	ll k; cin >> k;
	vector<ll> t(n), x(n), c(n);
	vector<tuple<ll,ll,ll>> f(n);
	rep(i,0,n) cin >> t[i];
	rep(i,0,n) cin >> x[i];
	rep(i,0,n) cin >> c[i];
	rep(i,0,n) f[i] = make_tuple(t[i], x[i], c[i]);
	sort(f.begin(), f.end());
	rep(i,0,n){
		t[i] = get<0>(f[i]);
		x[i] = get<1>(f[i]);
		c[i] = get<2>(f[i]);
	}

	vector<ll> dat(n);
	rep(i,0,n) dat[i] = x[i] - k * t[i];
	dat.push_back(0);
	sort(dat.begin(), dat.end());
	dat.erase(unique(dat.begin(), dat.end()), dat.end());

	auto get = [&](int i) -> int {
		ll g = x[i] - k * t[i];
		return lower_bound(dat.begin(), dat.end(), g) - dat.begin();
	};

	int m = dat.size();
	segtree<ll,op,e> seg(m);
	seg.set(lower_bound(dat.begin(), dat.end(), 0) - dat.begin(), 0);
	rep(i,0,n){
		int v = get(i);
		seg.set(v, max(seg.get(v), seg.prod(v, m) + c[i]));
	}
	cout << seg.all_prod() << '\n';
}