mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

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

    ans = 0
    for i, a in enumerate(A):
        ans += a * (i+1) * (N-i)
    print(ans)


if __name__ == '__main__':
    main()