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:
from math import factorial
mod = 10000007
line = raw_input().split(' ')
n = int(line[0])
r = int(line[1])
if n < r:
    print "-1"
else:
    n = n - r
    n = n + r - 1
    r = r - 1
    fac = factorial(n)
    fac /= factorial(r)
    fac /= factorial(n - r)
    fac %= mod
    print fac