#include<stdio.h>
#include<bitset>
#include<math.h>
using namespace std;
bitset<2000005> c;
int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	int n,i,j,lim;
	scanf("%d",&n);
	for(i=4;i<=n;i+=2)
		c[i]=1;
	c[0]=c[1]=1;
	lim=(int)sqrt((double)n);
	for(i=3;i<=lim;i+=2)
		if(!c[i])
			for(j=i*i;j<=n;j+=2*i)
				c[j]=1;
	int nr=0;
	for(i=1;i<=n;i++)
		if(!c[i])
			nr++;
	printf("%d\n",nr);
	return 0;
}