from sys import stdin


def main():
    input = lambda: stdin.readline()[:-1]
    N = int(input())
    A = list(map(int, input().split()))

    k = []
    for i in range(N):
        n = (N - i) * (i + 1)
        k.append(n)
    ans = 0
    for a, k in zip(A, k):
        ans += a * k
    print(ans)


main()