the question is very simple we just need to calculate total number of numbers which have exactly 4 divisors ↵
for ex 6, 8, 10↵
6--[1,2,3,6]↵
8--[1,2,4,8]↵
10--[1,2,5,10]↵
these are all of the forms p^3 or p*q ↵
but here n<=10^11
for ex 6, 8, 10
6--[1,2,3,6]↵
8--[1,2,4,8]↵
10--[1,2,5,10]↵
