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:
N, R = [int(i) for i in raw_input().split()]
grid = [[0]*N for i in range(R)]

for i in range(N):
	grid[0][i] = 1

for i in range(1, R):
	if N > i:
		sum_ = grid[i-1][i-1]
		for j in range(i, N):
			grid[i][j] = sum_
			sum_ = (sum_ + grid[i-1][j]) % 10000007
if grid[R-1][N-1] == 0:
	print "-1"
else:
	print grid[R-1][N-1]