#include <bits/stdc++.h>
using namespace std;
template <typename T>
ostream &operator<<(ostream &out, const vector<T> &v) {
  for (auto it : v) out << it << ' ';
  return out;
}
template <typename T>
istream &operator>>(istream &in, vector<T> &v) {
  for (auto &it : v) in >> it;
  return in;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &out, const pair<T1, T2> &p) {
  out << p.first << ' ' << p.second << ' ';
  return out;
}
template <typename T1, typename T2>
istream &operator>>(istream &in, pair<T1, T2> &p) {
  in >> p.first >> p.second;
  return in;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n, w, v, u;
  cin >> n >> w >> v >> u;
  bool bg = true;
  double ans = (double)w / u;
  for (int i = 0; i < n; i++) {
    int x, y;
    cin >> y >> x;
    double t = ((double)y / v);
    if (t * u < x) {
      bg = false;
    } else {
      ans = max(ans, t + ((double)w - x) / u);
    }
  }
  cout << fixed << setprecision(10);
  if (bg)
    cout << (double)w / u << endl;
  else
    cout << ans << endl;
  return 0;
}
