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
 
def ncr(n,r):
	if r > n-r:
		r = n-r;
	return math.factorial(n) / math.factorial(r) / math.factorial(n-r)
 
s = raw_input()
x = s.split(' ')
n = int(x[0])
r = int(x[1])
if n < r:
	print "-1"
else:
	print ncr(n-1,r-1) % 10000007