N = int(input())
A = [int(i) for i in input().split()]
# for i in range(N):
#     for j in range(i+1,N+1):
#         print("\t"*i + " ".join(map(str, A[i:j])))
s = 0
for i,n in enumerate(A):
    s += n*(N - i)*(i + 1)
print(s)