N, K = map(int, input().split())
A = list(map(int, input().split()))
mod = 10 ** 9 + 7

n = 505050

fact = [1] * (n + 1)
invfact = [1] * (n + 1)
for i in range(1, n):
    fact[i + 1] = ((i+1) * fact[i]) % mod
invfact[n] = pow(fact[n], mod - 2, mod)
for i in range(n - 1, -1, -1):
    invfact[i] = invfact[i + 1] * (i + 1) % mod

H = [1] * n
for i in range(n - 1):
    H[i + 1] = H[i] * (K + i + 1)
    H[i + 1] %= mod
for i in range(N + 1):
    H[i] *= invfact[i]
    H[i] %= mod

ans = 0
for i in range(N):
    ans += A[i] * H[i] * H[N - 1 - i]
    ans %= mod

print(ans)