#include <bits/stdc++.h>
using namespace std;
double w, mi = 1e9, ma = 0, x, y, dx, u, v;
int n, i;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n >> w >> v >> u;
  for (i = 0; i < n; i++) {
    cin >> x >> y;
    dx = x - y / u * v;
    if (mi > dx) mi = dx;
    if (ma < dx) ma = dx;
  }
  if (mi >= 0)
    cout << fixed << setprecision(6) << w / u;
  else
    cout << fixed << setprecision(6) << w / u + ma / v;
  return 0;
}
