#include <bits/stdc++.h>
using namespace std;
const double EPS = 1e-9;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  double u, v, w, x, y, l = 1e9, r = 0;
  cin >> n >> w >> v >> u;
  while (n--) {
    cin >> x >> y;
    l = min(l, x - y / u * v);
    r = max(r, x - y / u * v);
  }
  cout << fixed << setprecision(6) << w / u + r / v * (l < 0);
  return 0;
}
