#include<cstdio>
const int NMAX =(1<<16)+1;
unsigned char p[NMAX]={0};
int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	int i,j,nr=1,n;
	scanf("%d",&n);

	for(int i=1;((i*i)<<1)+(i<<1)<=n;++i)
		if(p[i]==0)		
			for(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;
}