abc034_C.py

W, H = map(int, input().split())
 
C = int(1e9)+7
 
fact = [1]
for x in range(1, H+W-1):
	fact.append( (x * fact[x-1]) % C )
	
factinv = [1] * (H+W-1)
factinv[H+W-2] = pow(fact[H+W-2], C-2, C)
 
for x in reversed(range(2, H+W-2)):
	factinv[x] = (factinv[x+1] * (x+1)) % C
 
def nCr(n, r):
	return (fact[n] * factinv[r] * factinv[n-r]) % C
 
print(nCr(H+W-2, H-1))