#include <bits/stdc++.h>
using namespace std;
int n;
double w, v, u, x, y, b, a = 1e99, t;
int main() {
  cin >> n >> w >> v >> u;
  while (n--) {
    cin >> x >> y;
    t = x / v + (w - y) / u;
    b = max(b, t), a = min(a, t);
  }
  if (a > w / u - 1e-9)
    printf("%.9lf", w / u);
  else
    printf("%.9lf", max(w / u, b));
}
