#include<stdio.h>
unsigned char c[125002];
int n,rez=1;
int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%d",&n);
	int i,j,i2;
	for(i=3; i*i<=n; i+=2)
	{
		if(c[i>>4]&(1<<((i>>1)&7)))
			continue;
		rez++;
		i2=i+i;
		for(j=i*i; j<=n; j+=i2)
			c[i>>4]|=1<<((j>>1)&7);
	}
	for(; i<=n; i+=2)
	{
		if(c[i>>4]&(1<<((i>>1)&7)))
			continue;
		rez++;
	}
	printf("%d\n",rez);
	return 0;
}