#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double w, v, u;
  cin >> n >> w >> v >> u;
  pair<double, double> p[n];
  double x, y;
  for (int i = 0; i < n; ++i) {
    cin >> x >> y;
    p[i] = make_pair(x, y);
  }
  double b[n];
  for (int i = 0; i < n; ++i) {
    b[i] = (double)u * p[i].first / v - p[i].second;
  }
  sort(b, b + n);
  if (b[0] >= 0 && b[n - 1] >= 0) {
    printf("%.8f", w / u);
  } else if (b[0] <= 0 && b[n - 1] <= 0) {
    printf("%.8f", w / u);
  } else {
    printf("%.8f", w / u + b[n - 1] / u);
  }
  return 0;
}
