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:
MOD = 10000007

def comb(n, r):
  if n < r:
    return -1

  if r == 0:
    return 1

  return ((n*comb(n-1, r-1))/r)

n, r = tuple(map(int, raw_input().split()))
ans = comb(n-1, r-1)

if ans > -1:
  print(comb(n-1, r-1)%MOD)
else:
  print(ans)