Building roads

There is a circle-shape lake in a beautiful town. And along the lake, there are N cities, living lots of pigs.
In 2008, the number of pigs is growing so faster that the government decide to transfer some pigs from some cities to others. And they want to make that each city has the same number of pigs.
Before the transfer, the government has to build some roads between cities. For example, if we want to move some pigs from city A to city B, we have to build a road between A and B. Now the government wants to save more money for the National's Day, so they want to build roads as few as possible, i.e, they want to know how many roads at least they have to build to make that each city has the same number of pigs.



Giving the initial number of pigs of each city, you should tell me the least number of roads have to build. If it is impossible to make each city has the same number of pigs, output "Impossible".

There will be multiple input sets. The first line of input will contain a integer K, means the number of sets.
Input for each set is a positive integer n(means the number of cities, 1 <= n <= 10000) on a line by itself, followed one line containing some positive integers(no more than 10000), indicate the cities' initial number of pigs.

Output for each input set should be one line containing a positive integer R, means the least number of roads have to build, output "Impossible" if it is impossible to make each city has the same number of pigs

4
3
1 2 3
3
2 2 2
4
1 3 1 3
3
1 3 3

1
0
2
Impossible

暑期集训队选拔赛（2）