Distribute Message

The contest’s message distribution is a big thing in prepare. Assuming N students stand in a row, from the row-head start transmit message, each person can transmit message to behind M personals, and how many ways could row-tail get the message?

Input may contain multiple test cases. Each case contains N and M in one line. (0<=M<N<=30)
When N=0 and M=0, terminates the input and this test case is not to be processed.

Output the ways of the Nth student get message.

4 1
4 2
0 0

1
3

4 1 : A->B->C->D
4 2 : A->B->C->D, A->C->D, A->B->D

威士忌

HZIEE 2007 Programming Contest