Find the number of ways of distributing N objects into R groups such that each group gets 1 or more objects.

Input:
The one and only line of input contains two numbers separated by a single space, which are N and R respectively.

Output:
The corresponding answer modulo 10000007 in a  single line and if no answer exist then print "-1".

Constraints:
1 ≤ N ≤ 100
1 ≤ R ≤ 100  

SAMPLE INPUT
4 2

SAMPLE OUTPUT
3

Explanation

Let the 2 groups be A and B respectively.
Case 1: A gets 1 object and B gets 3
Case 2: A gets 2 objects and B gets 2
Case 3: A gets 3 objects and B gets 1
import math

a,b=map(int,raw_input().split())
if(a>=b):
	a=a-1
	b=b-1
	i=math.factorial(a)
	j=math.factorial(b)
	k=math.factorial(a-b)
	ans=i/(j*k)
	print ans%10000007
else:
	print '-1'