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 modPow(a,b,c):
	x=1
	while (b>0):
		if(b%2==1):
			x=(x*a)%c
			
		a=(a*a)%c
		b=int(b/2)
	return x%c

fact=[0]*102
fact[0]=1
fact[1]=1

for i in range(2,102):
	fact[i]=(fact[i-1]*i)%mod
	#print "fact "+str(i)+" "+str(fact[i])

ifact=[0]*102
ifact[0]=1
ifact[1]=1

for i in range(2,102):
	ifact[i]=modPow(fact[i],9988439,mod)

def Comb(a,b):
	#print str(fact[a])+" "+str(ifact[b])+" "+str(ifact[a-b])
	c=fact[a]
	c=c*ifact[b]
	c=c%mod
	c=c*ifact[a-b]
	c=c%mod
	return c
	
n,r=map(int, raw_input().split())
#print str(n)+" "+str(r)
if n>=r:
	print Comb(n-1,r-1)
else :
	print "-1"