#include <bits/stdc++.h>
using namespace std;
long long n, m, k;
long long a[1000000], b[1000000], c[1000000], d[1000000];
int erfen(int w) {
  int l = 0, r = k + 1;
  while (r - l > 1) {
    int mid = (r + l) / 2;
    if (d[mid] <= w)
      l = mid;
    else
      r = mid;
  }
  return l;
}
int main() {
  int s, x;
  cin >> n >> m >> k;
  cin >> x >> s;
  for (int i = 1; i <= m; i++) {
    scanf("%I64d", &a[i]);
  }
  for (int i = 1; i <= m; i++) scanf("%I64d", &b[i]);
  for (int i = 1; i <= k; i++) scanf("%I64d", &c[i]);
  for (int i = 1; i <= k; i++) scanf("%I64d", &d[i]);
  int temp = erfen(s);
  long long minn = (n - c[temp]) * x;
  long long sum;
  for (int i = 1; i <= m; i++) {
    if (b[i] > s)
      continue;
    else {
      int rest = s - b[i];
      temp = erfen(rest);
      if (n - c[temp] <= 0)
        sum = 0;
      else
        sum = (n - c[temp]) * a[i];
      if (minn >= sum) minn = sum;
    }
  }
  printf("%I64d\n", minn);
}
