#include <bits/stdc++.h>
using namespace std;
int n;
double first[10005], second[10005], w, u, v;
double eps = 1e-9;
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(NULL), cout.tie(NULL);
  cin >> n >> w >> u >> v;
  for (int i = 0; i < n; i++) cin >> first[i] >> second[i];
  double ans = w / v;
  int fl = 0;
  for (int i = 0; i < n; i++) {
    if (first[i] > eps) fl = 1;
  }
  if (!fl) {
    cout << fixed << setprecision(15) << ans;
    return 0;
  }
  fl = 0;
  for (int i = 0; i < n; i++) {
    if (first[i] < eps) {
      fl = 1;
      break;
    }
    if (w - second[i] < eps) continue;
    double ti = first[i] / u;
    double hi = second[i] / v;
    if (hi - ti < eps) continue;
    fl = 1;
    break;
  }
  if (!fl) {
    cout << fixed << setprecision(15) << ans;
    return 0;
  }
  for (int i = 0; i < n; i++) {
    if (first[i] < eps) continue;
    if (w - second[i] < eps) continue;
    double j = first[i] / u;
    if (second[i] - w > eps) continue;
    double f = second[i] / v;
    if (f - j > eps) j = f;
    j += (w - second[i]) / v;
    ans = max(ans, j);
  }
  cout << fixed << setprecision(15) << ans;
  return 0;
}
