CF26A.Almost Prime

A number is called almost prime if it has exactly two distinct prime divisors. For example, numbers 6, 18, 24 are almost prime, while 4, 8, 9, 42 are not. Find the amount of almost prime numbers which are between 1 and n, inclusive.

一个数被称为“近似质数”，当且仅当它恰好有两个不同的质因数。例如，6、18、24 是近似质数，而 4、8、9、42 则不是。求在 $1$ 到 $n$（含端点）之间近似质数的个数。

Input contains one integer number n (1 ≤ n ≤ 3000).

输入包含一个整数 $ n $（$ 1 \leq n \leq 3000 $）。

Output the amount of almost prime numbers between 1 and n, inclusive.

输出在 1 到 $n$（含）之间的准素数（almost prime）的个数。