Video Surveillance

Description

A friend of yours has taken the job of security officer at the Star-Buy Company, a famous department store. One of his tasks is to install a video surveillance system to guarantee the security of the customers (er, and the security of the merchandise, of course!) on all of the store's countless floors. As the company has only a limited budget, there will be only one camera on each floor. However, each camera can turn to look in any direction.

The first problem is to choose where to install the camera on each floor. The only requirement is that every part of the room must be visible from there. In the following figure, the left floor can be completely surveyed from the position indicated by the dot. However, for the right floor, there is no such position! For example, the indicated position for the surveillance camera fails to see the lower left part of the floor.

Before trying to install the cameras, your friend first wants to know whether there is, indeed, suitable positions for them. He therefore asks you to write a program that, given a floor plan, determines whether there is a position from which the whole floor is visible. Each floor plan is a rectangular polygon, for which the edges do not intersect each other and only touch each other at the corners.

Input

The input file contains several floor descriptions. Each description starts with the number n of vertices that bound the floor (4 ≤ n ≤ 100). The next n lines contain two integers each: the x and y coordinates for the n vertices, given in clockwise order. All vertices will be distinct and at corners of the polygon. Thus, the edges alternate between horizontal and vertical.

A zero value for n indicates the end of the input.

Output

For each test case, first output a line with the number of the floor-plan case, as shown in the sample output. Then print a line stating ``Surveillance is possible.'' if there exists a position from which the entire floor can be observed, or print ``Surveillance is impossible.'' if there is no such position.

Print a blank line after each test case.

Sample Input

4
0 0
0 1
1 1
1 0
8
0 0
0 2
1 2
1 1
2 1
2 2
3 2
3 0
0

Sample Output

Floor #1
Surveillance is possible.

Floor #2
Surveillance is impossible.