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:
import math

def comb(n,r):
	if r> (n-r):
		r=n-r
	return math.factorial(n)/(math.factorial(r)*math.factorial(n-r))
	
	
p=raw_input()
n,r=[int(j) for j in p.split()]

if((n-r)<0):
	print "-1"
elif (n-r)==0:
	print "1"
else:
	#n=n-r
	print comb(n-1,r-1)%10000007