class Combinatorics:
	def __init__(self, n: int, mod: int) -> None:
		self.n = n
		self.mod = mod
		self.fa = [1] * (self.n + 1)
		self.fi = [1] * (self.n + 1)

		for i in range(1, self.n + 1):
			self.fa[i] = self.fa[i - 1] * i % self.mod

		self.fi[-1] = pow(self.fa[-1], self.mod - 2, self.mod)

		for i in range(self.n, 0, -1):
			self.fi[i - 1] = self.fi[i] * i % self.mod

	def comb(self, n: int, r: int) -> int:
		if n < r:return 0
		if n < 0 or r < 0:return 0
		return self.fa[n] * self.fi[r] % self.mod * self.fi[n - r] % self.mod

	def perm(self, n: int, r: int) -> int:
		if n < r:return 0
		if n < 0 or r < 0:return 0
		return self.fa[n] * self.fi[n - r] % self.mod
		
	def combr(self, n: int, r: int) -> int:
		if n == r == 0:return 1
		return self.comb(n + r - 1, r)
import typing
# 拡張Euclidの互除法
def extgcd(a: int, b: int, d: int = 0) -> typing.Tuple[int, int, int]:
	g = a
	if b == 0:
		x, y = 1, 0
	else:
		x, y, g = extgcd(b, a % b)
		x, y = y, x - a // b * y
	return x, y, g
 
# mod p における逆元
def invmod(a: int, p: int) -> int:
	x, y, g = extgcd(a, p)
	x %= p
	return x
n, k = map(int, input().split())
mod = 10 ** 9 + 7
C = Combinatorics(n, mod)
cnt = 1
for i in range(1, n + 1):
	cnt *= (k - i + 1)
	cnt *= invmod(i, mod)
	cnt %= mod
if k < n: cnt = 0
ans = 0
ans += cnt * C.comb(n - 1, 0)
for i in range(1, n + 1):
	cnt *= k + i
	cnt *= invmod(k + i - n, mod)
	cnt %= mod
	if k + i == n: cnt = 1
	ans += cnt * C.comb(n - 1, i)
	ans %= mod
print(ans % (mod))