#include <bits/stdc++.h>
using namespace std;
const int mx = 10010;
int a[mx], b[mx];
int main() {
  double w, n, v, u, t1, t2, t = 0, f = 0;
  cin >> n >> w >> v >> u;
  for (int i = 0; i < n; i++) {
    cin >> a[i] >> b[i];
    if (a[i] < 0)
      f = 1;
    else {
      t1 = b[i] / u;
      t2 = a[i] / v;
      if (t1 < t2) {
        t1 = t2 + (w - b[i]) / u;
        if (t < t1) t = t1;
      } else if (t1 > t2)
        f = 1;
    }
  }
  if (t && f)
    printf("%.10lf\n", t);
  else
    printf("%.10lf\n", w / u);
  return 0;
}
