package main

import . "fmt"

var b [1000000]bool

func main() {
	var n int64
	Scan(&n)
	c:=1
	n/=2
	for p:=int64(3);p<=n;p+=2 {
		if b[int(p)] {
			continue
		}
		c++
		n/=p
		for e:=p+p;int(e)<len(b);e+=p {
			b[int(e)]=true
		}
	}
	Println(c)
	
}