import sys


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    n = int(input())
    *a, = map(int, input().split())
    return sum((i + 1) * (n - i) * v for i, v in enumerate(a))


if __name__ == '__main__':
    ret = main()
    if ret is not None:
        print(ret)