#include <fstream.h>
long n,c,nd,x,nr,nnp;
ifstream fin ("ciur.in");
ofstream fout ("ciur.out");
int main ()
{
	fin>>n;
	nr=n;
	for (c=2;c<=n/2;c++)
	{
		nd=0;
		for (x=2;x*x<=c;x++)
			if (c%x==0)
				nd++;
			if (nd==0)
			{
				nnp=n/c;
				nr=nr-(np-1);
			}
	}
	fout<<nr;
	return 0;
}