#include <bits/stdc++.h>
using namespace std;
const int max_n = 1000000;
int n, m, k;
int x, s;
int a[max_n], b[max_n], c[max_n], d[max_n];
inline int max_complete(int money_left) {
  int l = 0, r = k;
  while (l < r) {
    int m = (l + r + 1) / 2;
    if (d[m] <= money_left)
      l = m;
    else
      r = m - 1;
  }
  return c[l];
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n >> m >> k;
  cin >> x >> s;
  a[0] = x;
  b[0] = 0;
  c[0] = 0;
  d[0] = 0;
  for (int i = 1; i <= m; i++) cin >> a[i];
  for (int i = 1; i <= m; i++) cin >> b[i];
  for (int i = 1; i <= k; i++) cin >> c[i];
  for (int i = 1; i <= k; i++) cin >> d[i];
  long long ans = 1LL * n * x;
  for (int i = 0; i <= m; i++) {
    int money_left = s - b[i];
    if (money_left < 0) continue;
    ans = min(ans, 1LL * (n - max_complete(money_left)) * a[i]);
  }
  cout << ans << endl;
  return 0;
}
