#include<stdio.h>
int n,rez=1;
unsigned char c[125010];
int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%d",&n);
	int i2;
	for(int i=3; i<=n; i+=2)
	{
		if(c[i>>4]&(1<<((i>>1)&7)))
			continue;
		rez++;
		for(int j=i+(i2=i<<1); j<=n; j+=i2)
			c[j>>4]|=1<<((j>>1)&7);
	}
	printf("%d\n",rez);
	return 0;
}