Migrated from Lutece 1521 Passing the Ball

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Description

There are N people passing the ball. It starts from the first person, and each time the person who gets the ball should pass the ball to another one. So what is the number of situations in which the ball is passed back to the first person after passing M times.

Input

Including two integers N and M, and N∈[2,9],M∈[1,15].

Output

The answer，and it does not exceed 2^31.

Samples

3 2

2

Resources

第八届ACM趣味程序设计竞赛第四场（正式赛）