S="ABCDEFG...XYZabcdefg...xyz"
Given two integers M and N, output all different possible sets of N characters from the first M characters in S. Print the sets in ASCII order(i.e. 'A'<'B'<'C'...<'Z'<'a'<'b'...<'z'). Each set should only be printed once, and the elements in the set should also be sorted in ASCII order.
For example, given M=3, N=2, you should output C(3,2)=3 lines, representing different sets of 2 characters from the set {A,B,C}(first 3 characters in S). The correct output is:
AB
AC
BC
Note that set {A,B} = {B,A}, thus should only be output once.
The first line of input contains a positive integer T(T<=30), which indicates the number of test case. For the next T lines, each line contains two positive integers M, N (M^N<10^7, M>=N).
case1: 1<=M<=10, 1<=N<=2
case2: 1<=M<=26, 1<=N<=10
case3: 1<=M<=52, 1<=N<=10
case4: 1<=M<=52, 1<=N<=20
For each test case, output all different possible sets of N characters from the first M characters in S. Each set a line, sorted in ASCII order.
Print a blank line after each test case.