#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const double PI = acos(-1.0);
const double epsilon = PI / 180.0;
long long powmod(long long a, long long b) {
  long long res = 1;
  a %= mod;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % mod;
    a = a * a % mod;
  }
  return res;
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
const int N = 5e5 + 10, M = 1e6 + 10;
double n, w, v, u;
double mx, mn;
int main() {
  cin >> n >> w >> v >> u;
  mx = -2e9;
  mn = 2e9;
  for (int i = 0; i < n; i++) {
    double x, y;
    cin >> x >> y;
    double t = x - y / u * v;
    mx = max(mx, t);
    mn = min(mn, t);
  }
  double ans = w / u;
  if (mn >= 0) {
    ans = w / u;
  } else {
    if (mx <= 0)
      ans = w / u;
    else
      ans = w / u + mx / v;
  }
  printf("%.10f\n", ans);
  return 0;
}
