彩色棒
You are given a bunch of wooden sticks. Each endpoint of each stick is colored with some color. Is it possible to align the sticks in a straight line such that the colors of the endpoints that touch are of the same color?
Input
the frist line have a number k(0<k<=10),that is the number of case. each case contais a number m,then have m line, each line contains two words, separated by spaces, giving the colors of the endpoints of one stick. A word is a sequence of lowercase letters no longer than 13 characters. There is no more than 250000 sticks.
Output
If the sticks can be aligned in the desired way, output a single line saying Possible, otherwise output Impossible.
Sample Input
1
5
blue red
red violet
cyan blue
blue magenta
magenta cyan
Sample Output
Possible