#include <bits/stdc++.h>
using namespace std;
int N, w, u, v;
int main() {
  int x, y;
  while (scanf("%d %d %d %d", &N, &w, &v, &u) != EOF) {
    double ans = 1.0 * w / u, lo = 0, hi = 0;
    for (int i = int(0); i < int(N); i++) {
      scanf("%d %d", &x, &y);
      double t = 1.0 * x / v - 1.0 * y / u;
      lo = min(t, lo);
      hi = max(hi, t);
    }
    if (lo < 0) ans += hi;
    printf("%.9f", ans);
  }
  return 0;
}
