MOD = 10 ** 9 + 7

fact_range = 2 * 10**6 + 100
fact = [1] * (fact_range + 1)
for i in range(0, fact_range):
    fact[i+1] = fact[i] * (i + 1) % MOD

ifact = [1] * (fact_range + 1)
ifact[fact_range] = pow(fact[fact_range], MOD - 2, MOD)
for i in range(fact_range, 0, -1):
    ifact[i-1] = ifact[i] * i % MOD

def comb(n, k):
    if k == 0:
        return 1
    if k < 0 or n < k:
        return 0
    else:
        return fact[n] * ifact[n-k] % MOD * ifact[k] % MOD

n, m = map(int, input().split())
s = [0] * (n + 2)
for i in range(n + 1)[::-1]:
    s[i] = s[i + 1] + comb(n, i)
    s[i] %= MOD

ans = s[m] * n % MOD
# print(ans)
# touch y = x + k
for k in range(1, n - m + 1):
    ans += s[m + k] # m + k <= n,  k <= n - m + 1
    ans %= MOD
    # print(k, ans, s[m + k], m - k)

# print('aa', ans)
t = [0] * (n + 2)
for i in range(n + 1)[::-1]:
    t[i] = t[i + 1] + comb(n, i) * max(0, 2 * i - n)
    t[i] %= MOD
u = [0] * (n + 2)
for i in range(n + 1)[::-1]:
    u[i] = u[i + 1] + comb(n, i) * max(0, 2 * i - n - 1)
    u[i] %= MOD

for k in range(1, n - m + 1):
    ans += t[m + k] - max(0, u[m + k - 1])
    ans %= MOD

print(ans)