N, p = map(int, input().split())
mod = 10**9 + 7
a1, a2 = 0, 1
acc, ans = 1, 1

if N <= 2:
    print(N-1)
    exit()

for i in range(2, N):
    a1, a2 = a2, (a2*p + a1) % mod
    acc = (acc + a2) % mod
    ans = (ans + a2 * acc) % mod

print(ans)