#include <iostream>
#include <iomanip>
#include <complex>
#include <vector>
#include <algorithm>
#include <cmath>
#include <array>
#include <map>
#include <queue>
using namespace std;
const double EPS = 1e-6;
const double INF = 1e12;
const double PI = acos(-1);
#define EQ(n,m) (abs((n)-(m)) < EPS)
#define X real()
#define Y imag()

typedef complex<double> P;
typedef vector<P> VP;
struct L : array<P, 2>{
    L(const P& a, const P& b){ at(0)=a; at(1)=b; }
    L(){}
};

namespace std{
    bool operator < (const P& a, const P& b){
        return !EQ(a.X,b.X) ? a.X<b.X : a.Y+EPS<b.Y;
    }
    bool operator == (const P& a, const P& b){
        return abs(a-b) < EPS;
    }
}

double dot(P a, P b){
    return (conj(a)*b).X;
}
double cross(P a, P b){
    return (conj(a)*b).Y;
}
int ccw(P a, P b, P c){
    b -= a;
    c -= a;
    if(cross(b,c) > EPS) return +1; //ccw
    if(cross(b,c) < -EPS) return -1; //cw
    if(dot(b,c) < -EPS) return +2; //c-a-b
    if(abs(c)-abs(b) > EPS) return -2; //a-b-c
    return 0; //a-c-b
}

bool intersectSS(const L& a, const L& b){
    return ( ccw(a[0],a[1],b[0]) *ccw(a[0],a[1],b[1]) <= 0 ) &&
        ( ccw(b[0],b[1],a[0]) *ccw(b[0],b[1],a[1]) <= 0 );
}
bool intersectSP(const L& s, const P &p){
    return abs(cross(s[0]-p, s[1]-p))<EPS  && dot(s[0]-p, s[1]-p)<EPS;
}

bool isParallel(const P &a, const P &b){
    return abs(cross(a,b)) < EPS;
}
bool isParallel(const L &a, const L &b){
    return isParallel(a[1]-a[0], b[1]-b[0]);
}
P crosspointLL(const L &l, const L &m) {
  double A = cross(l[1]-l[0], m[1]-m[0]);
  double B = cross(l[1]-l[0], l[1]-m[0]);
  return m[0] + B/A *(m[1]-m[0]);
}

int in_poly(const P &p, const VP &poly){
    int n = poly.size();
    int ret = -1;
    for(int i=0; i<n; i++){
        P a = poly[i]-p;
        P b = poly[(i+1)%n]-p;
        if(a.Y > b.Y) swap(a,b);
        if(intersectSP(L(a,b), P(0,0))) return 0;
        if(a.Y<=0 && b.Y>0 && cross(a,b)<0) ret = -ret;
    }
    return ret;
}

pair<vector<vector<int> >, VP> arrangement(const vector<L> &l){
    vector<VP> cp(l.size());
    VP plist;
    for(int i=0; i<(int)l.size(); i++){
        for(int j=i+1; j<(int)l.size(); j++){
            if(!isParallel(l[i], l[j]) && intersectSS(l[i], l[j])){
                P cpij = crosspointLL(l[i], l[j]);
                cp[i].push_back(cpij);
                cp[j].push_back(cpij);
                plist.push_back(cpij);
            }
        }
        cp[i].push_back(l[i][0]);
        cp[i].push_back(l[i][1]);
        plist.push_back(l[i][0]);
        plist.push_back(l[i][1]);
        sort(cp[i].begin(), cp[i].end());
        cp[i].erase(unique(cp[i].begin(), cp[i].end()), cp[i].end());
    }
    sort(plist.begin(), plist.end());
    plist.erase(unique(plist.begin(), plist.end()), plist.end());

    int n = plist.size();
    map<P, int> conv;
    for(int i=0; i<n; i++){
        conv[plist[i]] = i;
    }
    vector<vector<int> > adj(n);
    for(int i=0; i<(int)cp.size(); i++){
        for(int j=0; j<(int)cp[i].size()-1; j++){
            int jidx = conv[cp[i][j]];
            int jp1idx = conv[cp[i][j+1]];
            adj[jidx].push_back(jp1idx);
            adj[jp1idx].push_back(jidx);
        }
    }
    for(int i=0; i<n; i++){
        sort(adj[i].begin(), adj[i].end());
        adj[i].erase(unique(adj[i].begin(), adj[i].end()), adj[i].end());
    }
    return make_pair(adj, plist);
}


int main(){
    while(1){
        int n;
        cin >> n;
        if(n == 0) break;

        double vw,vc;
        cin >> vw >> vc;
        VP p(n);
        for(int i=0; i<n; i++){
            double x,y;
            cin >> x >> y;
            p[i] = P(x, y);
        }
        double xmin = p[0].X, xmax = p[n-1].X;
        VP poly = p;
        reverse(poly.begin(), poly.end());
        poly.push_back(P(xmin, -2e4));
        poly.push_back(P(xmax, -2e4));

        vector<L> l;
        for(int i=0; i<n; i++){
            if(i != n-1){
                l.push_back(L(p[i], p[i+1]));
            }
            double y = p[i].Y;
            L cut(P(xmin, y), P(xmax, y));
            VP cp;
            for(int j=0; j<n-1; j++){
                L edge(p[j], p[j+1]);
                if(!isParallel(cut, edge) && intersectSS(cut, edge)){
                    cp.push_back(crosspointLL(cut, edge));
                }
            }
            cp.erase(unique(cp.begin(), cp.end()), cp.end());
            int idx = lower_bound(cp.begin(), cp.end(), p[i]) -cp.begin();
            if(idx == (int)cp.size() || !(cp[idx] == p[i])){
                continue;
            }
            if(i > 0 && p[i-1].Y > p[i].Y +EPS && idx > 0){
                l.push_back(L(cp[idx-1], cp[idx]));
            }
            if(i < n-1 && p[i].Y +EPS < p[i+1].Y && idx < (int)cp.size()-1){
                l.push_back(L(cp[idx], cp[idx+1]));
            }
        }
        sort(l.begin(), l.end());
        l.erase(unique(l.begin(), l.end()), l.end());
        pair<vector<vector<int> >, VP> ret = arrangement(l);
        vector<vector<int> > &adj = ret.first;
        VP &plist = ret.second;

        vector<vector<pair<int, double> > > adj2(adj.size());
        for(int i=0; i<(int)adj.size(); i++){
            adj2[i].resize(adj[i].size());
            for(int j=0; j<(int)adj[i].size(); j++){
                P mid = (plist[i] +plist[adj[i][j]])/2.0;
                double cost;
                if(in_poly(mid, poly) == 1){
                    cost = abs(plist[i] -plist[adj[i][j]]) /vc;
                }else{
                    cost = abs(plist[i] -plist[adj[i][j]]) /vw;
                }
                adj2[i][j] = make_pair(adj[i][j], cost);
            }
        }

        priority_queue<pair<double, int> > wait;
        wait.push(make_pair(0, 0));
        vector<double> mincost(adj2.size(), INF);
        mincost[0] = 0;
        while(!wait.empty()){
            double cost = -wait.top().first;
            int pos = wait.top().second;
            wait.pop();
            if(cost > mincost[pos] +EPS) continue;
            if(pos == (int)adj2.size()-1) break;
            for(int i=0; i<(int)adj2[pos].size(); i++){
                int npos = adj2[pos][i].first;
                double ncost = cost +adj2[pos][i].second;
                if(ncost +EPS < mincost[npos]){
                    mincost[npos] = ncost;
                    wait.push(make_pair(-ncost, npos));
                }
            }
        }
        cout << fixed << setprecision(10);
        cout << mincost[adj2.size()-1] << endl;
    }    
    return 0;
}



Measured memory_bytes: 3860