#include<fstream.h>
ifstream intrare ("ciur.in");
ofstream iesire ("ciur.out");
char v[2000004];
int main()
{
	int nr;
	long long unsigned j,i,n;
	intrare>>n;
	nr=1;
	for(i=2;i<=n;i++)
	{
		if(i%2==1) v[i]=0;
		else v[i]=1;
	}
	for(i=3;i<=n;i+=2)
	{
		if(v[i]==0)
		{
			for(j=i*i;j<=n;j+=i)
			{
				v[j]=1;
			}
			nr++;
		}
	}
	iesire<<nr;
	return 0;
}