// Maximum-TNT

#include <iostream>
#include <string>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <algorithm>
#include <fstream>
#include <complex>

using namespace std;

#define cin fin
const int BUFSIZE = 1024;
ifstream fin("video.txt");

#define re real()
#define im imag()
typedef complex<double> cmp_t;

vector<cmp_t> g_point;

int g_n;

double Gaiseki(cmp_t &a,cmp_t &b)
{
    return a.re * b.im - a.im * b.re;
}

int GetType(cmp_t v1,cmp_t v2)
{
    if(v1.re > 0)
	return 1;
    if(v1.im < 0)
	return 2;
    if(v1.re < 0)
	return 3;
    if(v1.im > 0)
	return 4;
    abort();
    return 0;
}

bool Solve()
{
    double lx,ly,ux,uy;
    lx = ly = INT_MIN;
    ux = uy = INT_MAX;
    for(int i = 0 ; i < g_n ; i++)
    {
	cmp_t v1 = g_point[i+1]-g_point[i];
	cmp_t v2 = g_point[i+2]-g_point[i+1];
	if(Gaiseki(v1,v2) > 0)
	{
	    int type = GetType(v1,v2);
	    if(type == 1)
	    {
		if(lx < g_point[i+1].re)
		    lx = g_point[i+1].re;
		if(uy > g_point[i+1].im)
		    uy = g_point[i+1].im;
	    }
	    if(type == 2)
	    {
		if(ux > g_point[i+1].re)
		    ux = g_point[i+1].re;
		if(uy > g_point[i+1].im)
		    uy = g_point[i+1].im;
	    }
	    if(type == 3)
	    {
		if(ux > g_point[i+1].re)
		    ux = g_point[i+1].re;
		if(ly < g_point[i+1].im)
		    ly = g_point[i+1].im;
	    }
	    if(type == 4)
	    {
		if(lx < g_point[i+1].re)
		    lx = g_point[i+1].re;
		if(ly < g_point[i+1].im)
		    ly = g_point[i+1].im;
	    }
	    if(lx > ux || ly > uy)
		return false;
	}
    }

    return true;
}

int main()
{
    int case_num = 1;
    while(cin >> g_n, g_n != 0)
    {
	g_point.clear();
	for(int i = 0 ; i < g_n ; i++)
	{
	    double x,y;
	    cin >> x >> y;
	    g_point.push_back(cmp_t(x,y));
	}
	g_point.push_back(g_point[0]);
	g_point.push_back(g_point[1]);

	cout << "Floor #" << case_num++ << endl;
	cout << "Surveillance is ";
	if(Solve())
	    cout << "possible." << endl;
	else
	    cout << "impossible." << endl;
	cout << endl;
    }

    return 0;
}