Enumerating combinations
                            -------------------------

In this problem you are required to output in lexicographic order all k-combinations
of a set of n elements. For simplicity, assume that the n elements are numbers
from 0 through n-1.

Recall that the number of such combinations is equal to the combinatorial 
symbol C(n,k) (aka "n choose k"). It is equal to n!/(k!(n-k)!)

Since this number can be very large, your program only needs to work for
1 <= k <= n <= 16.

Input
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The input consists of several datasets. The first line of the input contains 
the number of datasets. Each line contains two integers separated by a blank -
n and k in that order.

Output
------

For each dataset print a list of all possible combinations in ascending 
lexicographic order.

Print a blank line BETWEEN datasets.

Sample Input
------------
2
4 2
7 1
Sample Output
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0,1
0,2
0,3
1,2
1,3
2,3

0
1
2
3
4
5
6