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 nCr(n,r):
    f = math.factorial
    return f(n) / f(r) / f(n-r)

x=raw_input("");
x=x.split(" ");
n=int(x[0])
r=int(x[1])

if (n<r):
    print "-1"
elif (n==r):
    print "1"
else:
    w=nCr(n-1,r-1)
    w=w%10000007;
    print w;