def accumulate_sum(start: int, end: int) -> int:
    if start > end:
        return 0
    return (end * (end + 1) - start * (start - 1)) // 2


def main():
    N = int(input())
    A = list(map(int, input().split()))

    if N == 1:
        print(A[0])
        return

    coefficients = []
    if N % 2 == 0:
        for t in range(1, N//2 + 1):
            coefficients.append(2*(N//2 - t)*t + 2*accumulate_sum(1, t))

        coeff_rev = reversed(coefficients)
        coefficients.extend(coeff_rev)
    else:
        for t in range(1, (N+1)//2):
            coefficients.append(t*(N - 2*(t-1)) + 2*accumulate_sum(1, t-1))
        coeff_rev = reversed(coefficients)
        coefficients.append((N+1)//2 + 2*accumulate_sum(1, (N+1)//2 - 1))
        coefficients.extend(coeff_rev)

    print(sum(A_elm * coeff for A_elm, coeff in zip(A, coefficients)))
    # Nが奇数 (N+1)//2=nとすると
    # 中央 n*1 + 2*sum(1, n-1)
    # 一つ横 (n-1)*3 + 2*sum(1, n-2)
    # 二つ横 (n-2)*5 + 2*sum(1,n-3)


    # Nが偶数 N//2=nとすると
    # 中央
    # 中央2つ n*0 + 2*sum(1,n)
    # 一つ横  (n-1)*2 + 2*sum(1,n-1)
if __name__ == "__main__":
    main()