#include<fstream>
#define Max 2000000

using namespace std;

long n,p;
long c[Max];

void umplere(long a)
{
	long i,x;
	x = a;
	for(i = x+1; i <= n; i++)
	{	
		if(i%x == 0)
		{
			c[i] = 1;
		}
	}
}
int main()
{
ifstream fin("ciur.in");
ofstream fout("ciur.out");
long i;
fin>>n;
for(i = 2; i <= n ;i++)
	if(c[i] == 0)
	{
		p = p+1;
	umplere(i);
	}
fout<<p<<"\n";
fin.close();
fout.close();
return 0;

}