Definition
----------

> 
> A square-free semiprime is a natural number that is the product of two distinct prime numbers.
> 
> 
> 

The task
--------

Given a natural number `n`, count all square-free semiprimes less than or equal to `n`.

Details
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Please write a function or procedure that accepts a single integer parameter and counts all square-free semiprimes less than or equal to its parameter. The count must either be a return value of a function call or be printed to STDOUT.

Scoring
-------

The answer with the fewest number of characters wins.

In the event of a tie, the following criteria will be used in order:

1. Tallest person
2. Best [time-complexity](/questions/tagged/time-complexity "show questions tagged 'time-complexity'")
3. Worst [space-complexity](/questions/tagged/space-complexity "show questions tagged 'space-complexity'")

Examples
--------

```
f(1)     = 0
f(62)    = 18
f(420)   = 124
f(10000) = 2600

```