#include <bits/stdc++.h>
using namespace std;
const double Pi = acos(-1.0);
int main() {
  if (fopen("data.in", "r")) freopen("data.in", "r", stdin);
  int N, W, V, U;
  bool doesnot = true;
  double arr[10011][2], ans = 0;
  scanf("%d", &N);
  scanf("%d", &W);
  scanf("%d", &V);
  scanf("%d", &U);
  for (int i = 0; i < N; i++) {
    scanf("%lf", &arr[i][0]);
    scanf("%lf", &arr[i][1]);
    doesnot &= (arr[i][0] / V) >= (arr[i][1] / U);
    ans = max(ans, (W - arr[i][1]) / U + (arr[i][0] / V));
  }
  if (doesnot)
    printf("%.10lf", (double)W / U);
  else
    printf("%.10lf", max(ans, (double)W / U));
  return 0;
}
