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Permutation

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Description:

       Permutation plays a very important role in Combinatorics.

For example,1 2 3 4 5 and 1 3 5 4 2 are both 5-permutations.

As everyone's known, the number of n-permutations is n!.

According to their magnitude relatives , if we insert the symbols "<" or ">" between every pairs of consecutive numbers of a permutation, we can get the permutation with symbols.

For example ,1 2 3 4 5 can be changed to 1<2<3<4<5.

1 3 5 4 2 can be changed to 1<3<5>4>2.

Now it’s your task to calculate the number of n-permutations with k ”<”symbols.

Maybe you don’t like large numbers , so you should just give the result mod 2007.

Input:

Input may contain multiple test cases.

Each test case is a line contains two integer n and k . 0<n<=100 and 0<=k<=100.

The input will terminated by EOF.

Output:

The nonnegative integer result mod 2007 on a line.

Sample Input:

5 2

Sample Output:

66

Note:

本题由旧版NOJ导入,来源:NUPT ACM

Info

NOJ

Provider NOJ

Code NOJ1137

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Date 04/20/2019 10:03:10

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