#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

FILE* input;
int upMax, downMin, rightMin, leftMax;
int upMaxI = 0, downMinI = 0, rightMinI = 0, leftMaxI = 0;

int max (int a, int b)
{
  if (a < b)
    return b;
  else
    return a;
}

int min (int a, int b)
{
  if (a < b)
    return a;
  else
    return b;
}

void wall (int prevX, int prevY, int curX, int curY)
{
  if (prevX == curX) // vert
    {
      if (curY > prevY) //up
	{
	  if (upMaxI == 0)
	    {
	      upMax = curX;
	      upMaxI = 1;
	    }
	  else
	    upMax = max (upMax, curX);
	}
      else // down
	{
	  if (downMinI == 0)
	    {
	      downMinI = 1;
	      downMin = curX;
	    }
	  else
	    downMin = min (downMin, curX);
	}
    }
  else // horz
    {
      if (curX > prevX)
	{
	  if (rightMinI == 0)
	    {
	      rightMinI = 1;
	      rightMin = curY;
	    }
	  else
	    rightMin = min (rightMin, curY);
	}
      else
	{
	  if (leftMaxI == 0)
	    {
	      leftMaxI = 1;
	      leftMax = curY;
	    }
	  else
	    leftMax = max (leftMax, curY);
	}
    }
}

void handle(int n)
{
  int firstX, firstY, curX, curY, prevX, prevY;
  fscanf (input, " %d %d", &curX, &curY);
  firstX = curX;
  firstY = curY;
  for (int line = 1; line < n; line++)
    {
      prevX = curX;
      prevY = curY;
      fscanf (input, " %d %d", &curX, &curY);
      wall (prevX, prevY, curX, curY);
    }
  wall (curX, curY, firstX, firstY);
  if (upMax <= downMin && leftMax <= rightMin)
    printf ("Surveillance is possible.\n");
  else
    printf ("Surveillance is impossible.\n");
}

int main()
{
  input = fopen("video.in", "r");
  for (int p = 0;; p++)
    {
      int n;
      fscanf (input, "%d", &n);
      if (n == 0) break;
      printf("Floor #%d\n", p + 1);
      handle(n);
      printf("\n");
    }
  return 0;
}