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 fac(n):
   if n == 1:
       return n
   else:
       return n*fac(n-1)
ar=map(int,raw_input().split())
if(ar[1]>ar[0]):
    print -1
    exit()
    
if(ar[1]==ar[0]):
    print 1
    exit()

if(ar[1]==1):
    print 1
    exit()
    
ar[0]=ar[0]-1
ar[1]=ar[1]-1
tmp=ar[0]-ar[1]
y=fac(tmp)*fac(ar[1])
x=fac(ar[0])/y
print x%10000007