ZL's Prob.2

发布时间: 2017年6月19日 00:24   时间限制: 1000ms   内存限制: 128M

< The Phantom of the Opera> is coming soon.
However we have come across some trouble.
The price of one ticket is p.  
Now there are n clients waiting out for tickets with exact p money in each of them. However, m other clients are waiting for tickets with undetachable 2p money each.(n>=m)
What's worse, our ticket center doesn't have change worth money p(in fact we don't have any money at the beginning T T).
We want you to help us conquer this problem:how many arrangements are there, to make the whole saling progress successfully running?
(No other people will join in beside those n+m person.)

There are muliply test cases.
For each test case,
there is only a line contains the two natural numbers n,m separated by blanks.(n>=m)
 As you can observe, n and m are both at least 1.

The each output will contain its own answer.
You may safely assume that each answer fits into a 64-bit unsigned integer.

4 3
2 1