import random
n = int(input())
a = list(map(int, input().split()))


# n = random.randrange(1, 100)
# a = [random.randrange(0, 10)for i in range(n)]
    
ans = 0
for i in range(n):
    l_cnt = i + 1
    r_cnt = n - i
    ans += a[i] * l_cnt * r_cnt
print(ans)

"""
# 愚直
res = 0
for i in range(n):
    for j in range(i, n):
        res += sum(a[i:j + 1])
print(res)
"""