#include <bits/stdc++.h>
using namespace std;
int upperbound(int sz, vector<int> &v, int val) {
  int low = 0;
  int high = sz - 1;
  int mid;
  while (high >= low) {
    mid = (high + low) / 2;
    if (v[mid] > val)
      high = mid - 1;
    else {
      if (mid + 1 == sz || v[mid + 1] > val) return mid;
      low = mid + 1;
    }
  }
  return -1;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, m, k, x, mana;
  cin >> n >> m >> k >> x >> mana;
  vector<int> typefmana(m), typeftime(m);
  vector<int> typesmana(k), typesspells(k);
  for (int i = 0; i < m; i++) cin >> typeftime[i];
  for (int i = 0; i < m; i++) cin >> typefmana[i];
  for (int i = 0; i < k; i++) cin >> typesspells[i];
  for (int i = 0; i < k; i++) cin >> typesmana[i];
  long long mintime = n * 1LL * x;
  int i = upperbound(k, typesmana, mana);
  long long ctime = mintime;
  if (i >= 0) ctime = max(0, n - typesspells[i]) * 1LL * x;
  mintime = min(mintime, ctime);
  int instant;
  for (int f = 0; f < m; f++) {
    if (typefmana[f] > mana || typeftime[f] >= x) continue;
    instant = 0;
    i = upperbound(k, typesmana, mana - typefmana[f]);
    if (i >= 0 && typesmana[i] <= mana - typefmana[f]) {
      instant = typesspells[i];
    }
    ctime = max(0, n - instant) * 1LL * typeftime[f];
    mintime = min(mintime, ctime);
  }
  cout << mintime << endl;
  return 0;
}
