#include<stdio.h>
const int N=1000000;
bool c[N];
int s;

int prim(int x)
{
	int j;
	if(x==2) return false;
	else
		if(x%2==0) return true;
	for(j=3;j*j<=x;j+=2)
	{
		if(x%j==0)
		{
			return true;
			break;
		}
	}
	return false;
}

int main()
{
	int i,j,n;
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%d",&n);
	for(i=2;i*i<=N;i++)
	{
		if(prim(i)==false)
			for(j=i*i;j<=n;j+=i)
				c[j]=true;
			
	}
	for(i=2;i*i<=N;i++)
		if(c[i]==false)
			s++;
	printf("%d",s);
	return 0;
}