N = int(input())
lsA = list(map(int,input().split()))
k = N
k1 = N
lsk = []
for i in range(N):
    lsk.append(k1)
    k -= 2
    k1 += k
ans = 0
for i in range(N):
    ans += lsA[i]*lsk[i]
print(ans)