#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  double w, v, u;
  cin >> n >> w >> v >> u;
  double maxi = 0, mini = 1e10;
  for (long long i = 0; i < n; i++) {
    double a, b;
    cin >> a >> b;
    maxi = max(maxi, a - v * b / u);
    mini = min(mini, a - v * b / u);
  }
  if (mini >= 0)
    printf("%.7lf", w / u);
  else
    printf("%.7lf", (maxi / v) + (w / u));
  return 0;
}
