#include <bits/stdc++.h>
using namespace std;
const double esp = 1e-6;
const double INF = 1e15;
int n;
double w, v, u;
double mi = INF, ma = 0;
int main() {
  scanf("%d%lf%lf%lf", &n, &w, &v, &u);
  for (int i = 1; i <= n; i++) {
    int x, y;
    scanf("%d%d", &x, &y);
    double t = y / u;
    double dis = x - t * v;
    ma = max(ma, dis);
    mi = min(mi, dis);
  }
  double ans;
  if (mi >= 0)
    ans = w / u;
  else if (ma <= 0)
    ans = w / u;
  else
    ans = ma / v + w / u;
  printf("%.10lf\n", ans);
  return 0;
}
