#include<cstdio>
#define NMAX 2000005
unsigned char p[NMAX]={0};
int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	int nr=1,n;
	scanf("%d",&n);
	//printf("%d\n",NMAX);
	for(int i=1;((i*i)<<1)+(i<<1)<=n;++i)
		if(p[i]==0)		
			for(int j=((i*i)<<1)+(i<<1);(j<<1)+1<=n;j+=(i<<1)+1)
				p[j]=1;
		
		for(int i=1;(i<<1)+1<=n;++i)
			if(p[i]==0)
				{				
					++nr;
				}
		printf("%d ",nr);
		return 0;
}