#include <iostream>
#include <iomanip>
#include <complex>
#include <vector>
#include <algorithm>
#include <cmath>
#include <array>
using namespace std;
const double EPS = 1e-10;
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
}

P projection(const L& l, const P& p) {
    double t = dot(p-l[0], l[0]-l[1]) / norm(l[0]-l[1]);
    return l[0] + t*(l[0]-l[1]);
}
double distanceLP(const L &l, const P &p) {
    return abs(cross(l[1]-l[0], p-l[0])) /abs(l[1]-l[0]);
}

bool intersectLS(const L& l, const L& s){
    return cross(l[1]-l[0], s[0]-l[0])*
        cross(l[1]-l[0], s[1]-l[0]) < EPS;
}
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;
}
double getarea(const VP &poly){
    int n = poly.size();
    double ret = 0;
    for (int i=0; i<n; i++){ 
        ret += cross(poly[i], poly[(i+1)%n]);
    }
    return ret*0.5;
}

double solve(const VP& poly){
    int n = poly.size();
    double ret = 0;
    vector<L> cand;
    for(int i=0; i<n; i++){
        for(int j=i+1; j<n; j++){
            cand.emplace_back(poly[i], poly[j]);
        }
        for(int j=0; j<n; j++){
            L edge(poly[j], poly[(j+1)%n]);
            if(distanceLP(edge, poly[i]) > EPS){
                cand.emplace_back(poly[i], projection(edge, poly[i]));
            }
        }
    }

    for(L &line: cand){
        VP plist;
        for(int k=0; k<n; k++){
            L edge(poly[k], poly[(k+1)%n]);
            if(!isParallel(line, edge) && intersectLS(line, edge)){
                plist.push_back(crosspointLL(line, edge));
            }
        }
        sort(plist.begin(), plist.end());
        plist.erase(unique(plist.begin(), plist.end()), plist.end());
        
        plist.emplace_back(INF, 0);
        double range = 0;
        for(int i=0; i<(int)plist.size()-1; i++){
            if(in_poly((plist[i] +plist[i+1]) /2.0, poly) >= 0){
                range += abs(plist[i+1] -plist[i]);
            }else{
                ret = max(ret, range);
                range = 0;
            }
        }
    }
    return ret;
}

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

        VP p(n);
        for(int i=0; i<n; i++){
            double x,y;
            cin >> x >> y;
            p[i] = P(x, y);
        }
        cout << fixed << setprecision(10);
        cout << "Case " << dn << ": " << solve(p) << endl;
        
    }
    return 0;
}


Measured memory_bytes: 4048