//Result:wizmann 1474 Accepted 764K 0MS G++ 3850B
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;
#define print(x) cout<<x<<endl
#define input(x) cin>>x
#define SIZE 128
#define pb push_back
const double eps=1e-10;
inline int zero(double x)
{
if(x<-eps) return -1;
else if(fabs(x)<eps) return 0;
else return 1;
}
struct point
{
double x,y;
point(){}
point(double i_x,double i_y)
{
x=i_x;y=i_y;
}
void setpoint(double i_x,double i_y)
{
x=i_x;y=i_y;
}
friend bool operator == (const point& pa,const point& pb)
{
return zero(pa.x-pb.x) && zero(pa.y-pb.y);
}
};
struct segment
{
point p1,p2;
segment(){}
segment(double x1,double y1,double x2,double y2)
{
p1.setpoint(x1,y1);
p2.setpoint(x2,y2);
}
segment(point t1,point t2){p1=t1;p2=t2;}
inline void setsegment(point a,point b){p1=a;p2=b;}
inline void setsegment(double x1,double y1,double x2,double y2)
{
p1.setpoint(x1,y1);
p2.setpoint(x2,y2);
}
};
struct line
{
double a,b,c;
friend bool operator == (const line x,const line y)
{
if(fabs(x.a-y.a)<eps&&fabs(x.b-y.b)<eps&&fabs(x.c-y.c)<eps) return true;
else return false;
}
inline void setline(double ta,double tb,double tc)
{
a=ta;b=tb;c=tc;
}
};
double xmult(point sp,point ep,point op)
{
return((sp.x-op.x)*(ep.y-op.y)-(sp.y-op.y)*(ep.x-op.x));
}
line makeLine(point p1,point p2)
{
line res;
int sig=1;
res.a=p2.y-p1.y;
if(res.a<0)
{
sig=-1;
res.a=sig*res.a;
}
res.b=sig*(p1.x-p2.x);
res.c=sig*(p1.y*p2.x-p2.y*p1.x);
return res;
}
line makeLine(segment s)
{
return makeLine(s.p1,s.p2);
}
bool lineIntersect(line l1,line l2,point &p)
{
double d=l1.a*l2.b-l2.a*l1.b;
if(fabs(d)<eps) return false;
else
{
p.x = (l2.c*l1.b-l1.c*l2.b)/d;
p.y = (l2.a*l1.c-l1.a*l2.c)/d;
return true;
}
}
bool segIntersect(segment l1,segment l2,point &p)
{
if((max(l1.p1.x,l1.p2.x)>=min(l2.p1.x,l2.p2.x))&&
(max(l1.p1.y,l1.p2.y)>=min(l2.p1.y,l2.p2.y))&&
(max(l2.p1.x,l2.p2.x)>=min(l1.p1.x,l1.p2.x))&&
(max(l2.p1.y,l2.p2.y)>=min(l1.p1.y,l1.p2.y))&&//快速排斥实验
fabs((xmult(l1.p1,l2.p1,l2.p2)*xmult(l1.p2,l2.p1,l2.p2))<=eps)&&
fabs((xmult(l2.p1,l1.p1,l1.p2)*xmult(l2.p2,l1.p1,l1.p2))<=eps))//跨立实验
{
lineIntersect(makeLine(l1),makeLine(l2),p);
return true;
}
else return false;
}
struct polygen
{
point pvec[SIZE];
point core[SIZE];
int sz;//kernel points
polygen(){sz=0;}
inline void push_point(const point& p)
{
pvec[sz++]=p;
}
void Cut(segment s)
{
int q=0;
//print(sz);
for(int i=0;i<sz;i++)
{
if(xmult(pvec[i],s.p2,s.p1)>=0)
{
//因为线段是顺时针给出的，如果是逆时针就是<=0
core[q++]=pvec[i]; //若是则存储
}
else
{
point cp;
if(xmult(pvec[i],s.p2,s.p1) * xmult(pvec[(i+1)%sz],s.p2,s.p1)<0)
{
point cp;
line l1=makeLine(s);
line l2=makeLine(pvec[i],pvec[(i+1)%sz]);
lineIntersect(l1,l2,cp);
core[q++]=cp;
}
}
}
//最后的p数组存放半平面的点集合
for(int i=0;i<q;i++)
{
pvec[i]=core[i];
}
//print("CORE: "<<core.size());
sz=q;
//print(sz);
}
void getKernel()
{
int n=sz;
point p[SIZE];
for(int i=0;i<n;i++) p[i]=pvec[i];
for(int i=0;i<n;i++)
{
segment s(p[i],p[(i+1)%n]);
Cut(s);
}
}
};
int n;
polygen poly;
int main()
{
double a,b;
int cas=1;
while(input(n) && n)
{
poly=polygen();
for(int i=0;i<n;i++)
{
scanf("%lf%lf",&a,&b);
poly.push_point(point(a,b));
}
poly.getKernel();
printf("Floor #%d\n",cas++);
if(poly.sz>0) print("Surveillance is possible.");
else print("Surveillance is impossible.");
puts("");
}
return 0;
}
