#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 1000;
const int MAX_Y = 10000;
const int MIN_Y = -10000;
const int NUM_Y = (MAX_Y - MIN_Y + 1);

const double INF = 1e70;

/* typedef */

typedef pair<double,int> pdi;
typedef stack<pdi> spdi;

template <typename T>
struct Pt {
  T x, y;

  Pt() {}
  Pt(T _x, T _y) : x(_x), y(_y) {}
  Pt(const Pt& pt) : x(pt.x), y(pt.y) {}

  bool operator==(const Pt pt) const { return x == pt.x && y == pt.y; }
  Pt<T> operator+(const Pt pt) const { return Pt<T>(x + pt.x, y + pt.y); }
  Pt<T> operator-() const { return Pt<T>(-x, -y); }
  Pt<T> operator-(const Pt pt) const { return Pt<T>(x - pt.x, y - pt.y); }
  Pt<T> operator*(T t) const { return Pt<T>(x * t, y * t); }
  Pt<T> operator/(T t) const { return Pt<T>(x / t, y / t); }
  T dot(Pt v) const { return x * v.x + y * v.y; }
  T cross(Pt v) const { return x * v.y - y * v.x; }
  Pt<T> mid(const Pt pt) { return Pt<T>((x + pt.x) / 2, (y + pt.y) / 2); }
  T d2() { return x * x + y * y; }
  double d() { return sqrt(d2()); }

  Pt<T> rot(double th) {
    double c = cos(th), s = sin(th);
    return Pt<T>(c * x - s * y, s * x + c * y);
  }

  bool operator<(const Pt& pt) const {
    return x < pt.x || (x == pt.x && y < pt.y);
  }

  void print(string format) {
    printf(("(" + format + ", " + format + ")\n").c_str(), x, y);
  }
  void print() { print("%.6lf"); }
};

typedef Pt<double> pt;

struct Dig {
  int i;
  double t;
  Dig() {}
  Dig(int _i, double _t) : i(_i), t(_t) {}
};

typedef vector<Dig> vdg;

/* global variables */

int n;
double vw, vc;
pt pts[MAX_N];
double lens[MAX_N];
vdg digs[MAX_N];
double dp[MAX_N];

/* subroutines */

/* main */

int main() {
  for (;;) {
    cin >> n;
    if (n == 0) break;

    for (int i = 0; i < n; i++)
      digs[i].clear(), dp[i] = INF;
    
    cin >> vw >> vc;

    for (int i = 0; i < n; i++)
      cin >> pts[i].x >> pts[i].y;
    
    for (int i = 0; i < n - 1; i++)
      lens[i] = (pts[i + 1] - pts[i]).d();

    spdi ystk0, ystk1;

    for (int i = 0; i < n; i++) {
      while (! ystk0.empty() && ystk0.top().first > pts[i].y) ystk0.pop();

      if (! ystk0.empty()) {
	int j = ystk0.top().second;

	if (j < i - 1) {
	  double s0 = (pts[i].y - pts[j].y) / (pts[j + 1].y - pts[j].y);
	  double t0 =
	    (lens[j] * s0) / vw +
	    (pts[i].x - ((1 - s0) * pts[j].x  + s0 * pts[j + 1].x)) / vc;
	  digs[j].push_back(Dig(i, t0));
	}
      }

      ystk0.push(pdi(pts[i].y, i));
    }

    for (int i = n - 1; i >= 0; i--) {
      while (! ystk1.empty() && ystk1.top().first > pts[i].y) ystk1.pop();

      if (! ystk1.empty()) {
	int j = ystk1.top().second;

	if (j > i + 1) {
	  double s1 = (pts[i].y - pts[j].y) / (pts[j - 1].y - pts[j].y);
	  double t1 =
	    (lens[j - 1] * s1) / vw +
	    (((1 - s1) * pts[j].x  + s1 * pts[j - 1].x) - pts[i].x) / vc;
	  digs[i].push_back(Dig(j, t1));
	}
      }

      ystk1.push(pdi(pts[i].y, i));
    }

    dp[0] = 0.0;
    
    for (int i = 0; i < n - 1; i++) {
      double dp1 = dp[i] + lens[i] / vw;
      if (dp[i + 1] > dp1) dp[i + 1] = dp1;

      vdg& digi = digs[i];
      for (vdg::iterator vit = digi.begin(); vit != digi.end(); vit++) {
	double dpd = dp[i] + vit->t;
	if (dp[vit->i] > dpd) dp[vit->i] = dpd;
      }
    }

    printf("%.6lf\n", dp[n - 1]);
  }

  return 0;
}

Measured memory_bytes: 1404