Problem: 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

Solution (in PYTHON):

Solution:
def facto(n):
	res = 1
	if n < 1:
		return 1
	while n > 0:
		res = res * n
		n -= 1
	return res
n,r = raw_input().split()
n = int(n)
r = int(r)
if n < r:
	print -1
else:
		result = facto(n-1)/(facto(r-1)*facto(n-r))
		result = result % 10000007
		print result