#include <bits/stdc++.h>
using namespace std;
double x, y;
int main() {
  double n, w, v, u, i;
  double MAX = -1, MIN = 100000001;
  while (~scanf("%lf %lf %lf %lf", &n, &w, &v, &u)) {
    for (i = 0; i < n; ++i) {
      scanf("%lf %lf", &x, &y);
      MAX = max(MAX, x - (y * v) / u);
      MIN = min(MIN, x - (y * v) / u);
    }
    if (MIN >= 0)
      printf("%.10lf\n", w / u);
    else if (MIN < 0 && MAX >= 0)
      printf("%.10lf\n", w / u + MAX / v);
    else if (MAX < 0)
      printf("%.10lf\n", w / u);
  }
  return 0;
}
