N, K = map(int, input().split())
A = list(map(int, input().split()))
A.reverse()

mod = sum(A)
powk = [1] * N
for i in range(1, N):
    powk[i] = powk[i - 1] * K % mod

ans = 0
for a, k in zip(A, powk):
    ans += a * k
    ans %= mod
print(ans)