#28794: python新手解


abrian1014a@gmail.com (千空)


x=int(input())
y=[int(num) for num in input().split()]
Answer=0
for i in range(x):
   z=int(y[i])
   Answer=Answer+(z*(i+1))
print(Answer)
就是先搞個清單再用迴圈去搞就行了