#include <stdio.h>

int i,j,N,sol;
char p[125010];

int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);

	scanf("%d",&N);

	for(i=1;(((i*i)<<2)+(i<<2)+1)<=N;i++)
		if((p[i>>3]&(1<<(i&7)))==0)
			for(j=(((i*i)<<1)+(i<<1));((j<<1)+1)<=N;j+=((i<<1)+1))
				p[j>>3]|=(1<<(j&7));

	sol=1;
	for(i=1;((i<<1)+1)<=N;i++)
		if((p[i>>3]&(1<<(i&7)))==0) sol++;

	printf("%d\n",sol);

	return 0;
}