## Problem A: Drawing

One day, the Artful Coder saw an interesting shape. He immediately started
wondering if it would be possible to draw it on a piece of paper using a
pencil via one continuous line. After trying for several minutes, he eventually
gave up and started writing a program to automate the procedure.

Now, despite his name, the Artful Coder really isn't that good a programmer. He
doesn't know if his own program produces correct output, so he's looking for a
second opinion. Given a description of a shape, determine if it can be drawn in
one continuous motion of a pencil, without backtracking over any already-drawn
line segments. The shape will be given as a collection of straight line
segments, in no particular order, that can only touch at their endpoints.

### Input Format

The input consists of multiple shapes. Each shape begins with a single number
0 < **N** < 1000, which is the number of line segments in the shape.
There are then **N** lines following, each with four integers **a**,
**b**, **c**, and **d**, describing a line from **(a, b)** to
**(c, d)**. You may assume that at most one of **a = c** or **b = d**
will be true, and that -1000 < **a**,**b**,**c**,**d** <
1000.

The input will be terminated with a shape that has **N = 0**, which should
not be processed.

### Output Format

Output one line for each input shape, containing either "Impossible" or
"Possible" (without quotes).

### Sample Input

1
0 0 1 1
2
0 0 1 0
1 1 1 0
2
0 0 1 0
2 2 2 3
9
0 0 1 0
0 0 0 1
1 0 1 1
0 1 1 1
0 0 1 1
0 0 -5 -5
-5 -5 5 -5
5 -5 5 5
5 5 1 1
0

### Sample Output

Possible
Possible
Impossible
Possible

*Kent Williams-King*

**CCPC 2014**