#include<bits/stdc++.h>
 
#define REP(i,s,n) for(int i=s;i<n;i++)
#define rep(i,n) REP(i,0,n)
#define EPS (1e-8)
#define COUNTER_CLOCKWISE 1
#define CLOCKWISE -1 
#define ONLINE_BACK 2
#define ONLINE_FRONT -2
#define ON_SEGMENT 0
#define equals(a,b) (fabs((a)-(b)) < EPS)
 
using namespace std;
 
const int IINF = INT_MAX;

class Point{
public:
  double x,y;
  Point(double x = 0,double y = 0): x(x),y(y){}
  Point operator + (Point p){return Point(x+p.x,y+p.y);}
  Point operator - (Point p){return Point(x-p.x,y-p.y);}
  Point operator * (double a){return Point(a*x,a*y);}
  Point operator / (double a){return Point(x/a,y/a);}
  bool operator < (const Point& p) const{ return !equals(x,p.x)?x<p.x:y<p.y; }
  bool operator == (const Point& p)const{ return fabs(x-p.x) < EPS && fabs(y-p.y) < EPS; }
 };
 
struct Segment{
  Point p1,p2;
  Segment(Point p1 = Point(),Point p2 = Point()):p1(p1),p2(p2){}
  bool operator == (const Segment& p)const { return ( ( p.p1 == p1 && p.p2 == p2 ) || ( p.p1 == p2 && p.p2 == p1 ) ); }
};
 
typedef Point Vector;
typedef Segment Line;
typedef vector<Point> Polygon;
 
double dot(Point a,Point b){ return a.x*b.x + a.y*b.y; }
double cross(Point a,Point b){ return a.x*b.y - a.y*b.x; }
double norm(Point a){ return a.x*a.x+a.y*a.y; }
double abs(Point a){ return sqrt(norm(a)); }
 
int ccw(Point p0,Point p1,Point p2){
  Point a = p1-p0;
  Point b = p2-p0;
  if(cross(a,b) > EPS)return COUNTER_CLOCKWISE;
  if(cross(a,b) < -EPS)return CLOCKWISE;
  if(dot(a,b) < -EPS)return ONLINE_BACK;
  if(norm(a) < norm(b))return ONLINE_FRONT;
  return ON_SEGMENT;
}
 

bool intersectLS(Line l, Line s) {
  return cross(l.p2-l.p1, s.p1-l.p1)*       // s[0] is left of l
         cross(l.p2-l.p1, s.p2-l.p1) < EPS; // s[1] is right of l
}

bool intersectSS(Line s, Line t) {
  return ccw(s.p1,s.p2,t.p1)*ccw(s.p1,s.p2,t.p2) <= 0 &&
         ccw(t.p1,t.p2,s.p1)*ccw(t.p1,t.p2,s.p2) <= 0;
}
 
Point crosspoint(Line l,Line m){
  double A = cross(l.p2-l.p1,m.p2-m.p1);
  double B = cross(l.p2-l.p1,l.p2-m.p1);
  if(abs(A) < EPS && abs(B) < EPS){
    vector<Point> vec;
    vec.push_back(l.p1),vec.push_back(l.p2),vec.push_back(m.p1),vec.push_back(m.p2);
    sort(vec.begin(),vec.end());
    assert(vec[1] == vec[2]);
    return vec[1];
  }
  return m.p1 + (m.p2-m.p1)*(B/A);
}

double cross3p(Point p,Point q,Point r) { return (r.x-q.x) * (p.y -q.y) - (r.y - q.y) * (p.x - q.x); }
bool collinear(Point p,Point q,Point r){ return fabs(cross3p(p,q,r)) < EPS; }
bool ccwtest(Point p,Point q,Point r){ return cross3p(p,q,r) > 0; }
bool onSegment(Point p,Point q,Point r){
  return collinear(p,q,r) && equals(sqrt(pow(p.x-r.x,2)+pow(p.y-r.y,2)) + sqrt(pow(r.x-q.x,2) + pow(r.y-q.y,2) ),sqrt(pow(p.x-q.x,2)+pow(p.y-q.y,2)) ) ;
}

double angle(Point a,Point b,Point c){
  double ux = b.x - a.x, uy = b.y - a.y;
  double vx = c.x - a.x, vy = c.y - a.y;
  return acos((ux*vx + uy*vy)/sqrt((ux*ux + uy*uy) * (vx*vx + vy*vy)));
}  
   
bool inPolygon(Polygon poly,Point p){
  if((int)poly.size() == 0)return false;
  rep(i,poly.size()) if(onSegment(poly[i],poly[(i+1)%poly.size()],p)) return true;

  double sum = 0;
  for(int i=0; i < (int)poly.size() ;i++){
    if( equals(cross(poly[i]-p,poly[(i+1)%poly.size()]-p),0.0) ) continue; // ３点が平行だとangleがnanを返しsumがnanになり死ぬ
      if( cross3p(p,poly[i],poly[(i+1)%poly.size()]) < 0) sum -= angle(p,poly[i],poly[(i+1)%poly.size()]);
      else sum += angle(p,poly[i],poly[(i+1)%poly.size()]);
  }
  return (fabs(sum - 2*M_PI) < EPS || fabs(sum + 2*M_PI) < EPS);
}  
 
bool inPolygon(const Polygon &poly,Segment seg){
  vector<Point> vp;
  vp.push_back(seg.p1),vp.push_back(seg.p2);
  rep(i,(int)poly.size()) {
    Segment edge = Segment(poly[i],poly[(i+1)%(int)poly.size()]);
    if( equals(cross(seg.p1-edge.p1,seg.p2-edge.p2),0.0) ) {
      if( onSegment(seg.p1,seg.p2,edge.p1) ) vp.push_back(edge.p1);
      if( onSegment(seg.p1,seg.p2,edge.p2) ) vp.push_back(edge.p2);
    } else if( intersectSS(seg,edge) ) vp.push_back(crosspoint(seg,edge));
  }
  sort(vp.begin(),vp.end());
  vp.erase(unique(vp.begin(),vp.end()),vp.end());
  rep(i,(int)vp.size()-1) {
    Point middle_point = ( vp[i] + vp[i+1] ) / 2.0;
    if( !inPolygon(poly,middle_point) ) return false;
  }
  return true;
}
 
const int MAX_N = 110;
int N;
Point ps[MAX_N];
 
bool LTE(double a,double b) { return equals(a,b) || a < b ; } 
 
void compute(){
  vector<Point> poly;
  rep(i,N) poly.push_back(ps[i]);
  vector<Segment> segs;
  rep(i,N) segs.push_back(Segment(ps[i],ps[(i+1)%N]));
 
  double ans = 0;
  rep(i,N) REP(j,i+1,N) {
    Line line = Line(ps[i],ps[j]);
    vector<Point> cand;
    cand.push_back(line.p1),cand.push_back(line.p2);
    rep(k,N) {
      Segment seg = Segment(ps[k],ps[(k+1)%N]);
      if( !( line == seg ) && intersectLS(line,seg) && !equals(cross(line.p1-line.p2,seg.p1-seg.p2),0.0) ) cand.push_back(crosspoint(line,seg));
    }
    sort(cand.begin(),cand.end());
    cand.erase(unique(cand.begin(),cand.end()),cand.end());
    line.p1 = ps[i], line.p2 = ps[j];
    rep(k,(int)cand.size()) if( cand[k] == line.p1 ) {
      int pos = k;
      while( pos-1 >= 0 && inPolygon(poly,(line.p1+cand[pos-1])/2.0) ) line.p1 = cand[--pos];
      break;
    }
    rep(k,(int)cand.size()) if( cand[k] == line.p2 ) {
      int pos = k;
      while( pos+1 < cand.size() && inPolygon(poly,(line.p2+cand[pos+1])/2.0) ) line.p2 = cand[++pos];
      break;
    }

    bool failed = false;
    rep(k,N) {
      if( onSegment(line.p1,line.p2,segs[k].p1) || onSegment(line.p1,line.p2,segs[k].p2) ) continue;
      if( intersectSS(line,segs[k]) ) { 
        Point cp = crosspoint(line,segs[k]);
        if( cp == line.p1 || cp == line.p2 ) continue;
        failed = true; break; }
    }
    if( failed ) continue;
    if( !inPolygon(poly,line) ) continue;
    ans = max(ans,abs(line.p1-line.p2));
  }
  printf("%.8lf\n",ans);
}
 
int main(){
  int CNT = 1;
  while( scanf("%d",&N), N ){
    rep(i,N) scanf("%lf %lf",&ps[i].x,&ps[i].y);
    cout << "Case " << CNT++ << ": ";
    compute();
  }
  return 0;
}

Measured memory_bytes: 1412