#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;
}