#include <stdio.h>

FILE* f;
FILE* s;

char sir[2000000];

int main(void)
{
	f=fopen ("ciur.in","r");
	s=fopen ("ciur.out","w");

	long int n;
	fscanf (f,"%ld",&n);

	for (long int i=2;i<=n;i++)
	{
		for (long int j=i+i;j<=n;j+=i)
		{
			sir[j]='1';
		}
	}

	long int cnt=0;
	for (i=2;i<=n;i++)
	{
		if (sir[i]!='1')
			cnt++;

	}

	fprintf (f,"%ld",cnt);

	fcloseall();

	return 0;

}