n = int(input())
a_i = [int(x) for x in input().split()]

cumulative_sum = [0]

for i in range(n):
    cumulative_sum.append(cumulative_sum[i] + a_i[i])
    
ans = 0

for i in range(n + 1):
    ans += cumulative_sum[i] * (2 * i - n)

print(ans)