#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
const int N = 1e5 + 10;
int n, width, bussp, persp;
pair<int, int> a[N];
double solve() {
  bool okay = 1;
  for (int i = 1; i <= n && okay; i++)
    if (1LL * a[i].second * bussp > 1LL * a[i].first * persp) okay = 0;
  if (okay) return (width + .0) / persp;
  double ans = 0;
  for (int i = 1; i <= n; i++)
    ans = max(ans, max((a[i].first + .0) / bussp, (a[i].second + .0) / persp) +
                       (width - a[i].second + .0) / persp);
  return ans;
}
int main() {
  scanf("%d%d%d%d", &n, &width, &bussp, &persp);
  for (int i = 1; i <= n; i++) scanf("%d%d", &a[i].first, &a[i].second);
  printf("%.9f", solve());
}
