#include <algorithm>
#include <iostream>
#include <vector>
using ld = long double;
using namespace std;
int main() {
int n, k;
ld x;
vector<ld> p(k + 1);
vector<ld> t(k + 1);
cin >> n >> k >> x;
cin >> p[0];
vector<ld> s(n);
for (int i = 0; i < n; i++)
cin >> s[i];
for (int i = 1; i <= k; i++)
cin >> t[i];
for (int i = 1; i <= k; i++)
cin >> p[i];
int ans = 0;
sort(s.begin(), s.end());
int pt = n - 1;
for (int i = 0; i <= k; i++) {
while (s[pt] * (p[i] - t[i]) >= x) {
pt--;
}
}
cout << n - (pt + 1) << endl;
}