i need to do standard deviation on my calculator for my math class, but whenever i do it i get a wrong answer.

here is what i am doing

i enter the numbers in L1 and their frequency in L2 and then i do the formula

ex. 10,20,30,40,50,60 in L1

1,1,1,1,1,1 in L2

stdDev(L1L2)= 18.70828693

but the actual answer is 17.1