N = int(input())
A = tuple(map(int, input().split()))

T = [N] * N
for i in range(N // 2):
    T[i + 1] = T[i] + N - (i + 1) * 2
    T[N - i - 2] = T[i + 1]
print(sum(A[i]*T[i] for i in range(N)))