// 2008模擬地区予選 C : Dig or Climb

#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>

using namespace std;

int main(){
	int n;
	int x[1000], y[1000];
	double xd[3000], yd[3000], dist[3000];
	int next[3000];
	while(cin >> n, n){
		int vw, vc; cin >> vw >> vc;
		for(int i=0;i<n;i++){
			cin >> x[i] >> y[i];
			xd[i] = x[i];
			yd[i] = y[i];
			next[i] = -1;
		}
		int size = n;
		for(int i=0;i<n;i++){
			// 進行方向に掘り進める
			if(i+1 < n && y[i] < y[i+1]){
				for(int j=i+1;j+1<n;j++){
					if(y[j+1] == y[i]){
						next[i] = j+1;
						break;
					}
					if(min(y[j], y[j+1]) <= y[i] && y[i] <= max(y[j], y[j+1])){
						xd[size] = (y[i]-yd[j])*(xd[j+1]-xd[j])/(yd[j+1]-yd[j]) + xd[j];
						yd[size] = y[i];
						next[i] = size;
						next[size] = -1;
						size++;
						break;
					}
				}
			}
			// 逆方向に掘り進める
			if(i-1 >= 0 && y[i] < y[i-1]){
				for(int j=i-1;j-1>=0;j--){
					if(y[j-1] == y[i]){
						next[j-1] = i;
						break;
					}
					if(min(y[j], y[j-1]) <= y[i] && y[i] <= max(y[j], y[j-1])){
						xd[size] = (y[i]-yd[j])*(xd[j-1]-xd[j])/(yd[j-1]-yd[j]) + xd[j];
						yd[size] = y[i];
						next[size] = i;
						size++;
						break;
					}
				}
			}
		}
		vector< pair<double, int> > vp;
		for(int i=0;i<size;i++){
			dist[i] = 1e12;
			vp.push_back(make_pair(xd[i], i));
		}
		sort(vp.begin(), vp.end());
		dist[0] = 0;
		// 手前から最短経路を確定させていく
		for(int i=0;i+1<vp.size();i++){
			int pos  = vp[i].second;
			int npos = vp[i+1].second;
			dist[npos] = min(dist[npos], dist[pos] + hypot(xd[pos]-xd[npos], yd[pos]-yd[npos])/vw);
			if(next[pos] != -1)
				dist[next[pos]] = min(dist[next[pos]], dist[pos] + (xd[next[pos]] - xd[pos])/vc);
		}
		printf("%.8lf\n", dist[n-1]);
	}
}