mod = 10 ** 9 + 7
n, k = map(int, input().split())
fact = [1] * (n + 1)
permk = [1] * (n + 1)
for i in range(n):
    fact[i + 1] = fact[i] * (i + 1) % mod
    permk[i + 1] = permk[i] * (k - i) % mod
ifact = [1] * (n + 1)
ifact[n] = pow(fact[n], mod - 2, mod)
for i in range(n)[::-1]:
    ifact[i] = ifact[i + 1] * (i + 1) % mod
ans = sum(permk[n - i] * ifact[n - i] * fact[n - 1] * ifact[n - 1 - i] * ifact[i] * pow(2, n - 1 - i, mod) for i in range(n)) % mod
print(ans)