#include <bits/stdc++.h>
using namespace std;
using namespace placeholders;
using LL = long long;
using ULL = unsigned long long;
using VI = vector<int>;
using VVI = vector<vector<int> >;
using VS = vector<string>;
using SS = stringstream;
using PII = pair<int, int>;
using VPII = vector<pair<int, int> >;
template <typename T = int>
using VT = vector<T>;
template <typename T = int>
using VVT = vector<vector<T> >;
template <typename T = int>
using LIM = numeric_limits<T>;
template <typename T>
inline istream &operator>>(istream &s, vector<T> &v) {
  for (T &t : v) {
    s >> t;
  }
  return s;
}
template <typename T>
inline ostream &operator<<(ostream &s, const vector<T> &v) {
  for (int i = 0; i < int(v.size()); ++i) {
    s << (" " + !i) << v[i];
  }
  return s;
}
template <typename T>
inline T fromString(const string &s) {
  T res;
  istringstream iss(s);
  iss >> res;
  return res;
}
template <typename T>
inline string toString(const T &a) {
  ostringstream oss;
  oss << a;
  return oss.str();
}
template <typename T>
inline bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
inline bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
constexpr double INF = LIM<double>::max() / 10;
constexpr double EPS = 1e-9;
int N;
double W, V, U;
double X[1 << 14], Y[1 << 14];
double solve1() {
  for (int i = (int)(0); i < (int)(N); ++i) {
    const double T = X[i] / V;
    if (U * T < Y[i] - EPS) {
      return INF;
    }
  }
  return W / U;
}
double solve2() {
  double res = 0;
  for (int i = (int)(0); i < (int)(N); ++i) {
    double T = X[i] / V;
    double y = min(Y[i], U * T);
    chmax(res, T + (W - y) / U);
  }
  return res;
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << setprecision(12) << fixed;
  cin >> N >> W >> V >> U;
  for (int i = (int)(0); i < (int)(N); ++i) {
    cin >> X[i] >> Y[i];
  }
  cout << min(solve1(), solve2()) << endl;
  return 0;
}
