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
def factorial(n):
	i=1
	res=1
	while i <= n:
		res=res*i
		i=i+1
	return res
 
def main():
	a,b = raw_input().split()
	a=int(a)
	b=int(b)
	a=a-1
	b=b-1
	res=factorial(a)
	res=res/factorial(a-b)
	res=res/factorial(b)
	res=res%10000007
	if b>a:
		res=-1
	print(res)
 
main()