#include <stdio.h>
#define mx 1000010
long i,j,n;
long v[1010];
char p[mx];

void ciur(int max)
{
	long i;
	v[0]=1;
	for (i=1; i*i*2+2*i<=max; i++)
	{
		j=i*i*2+2*i;
		while (2*j+1<=max)
		{
			p[j]=1;
			j=j+2*i+1;
		}
	}
	for (i=(max-1)/2; i>0; i--)
		if (p[i]==0)
			v[0]++;
}

int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%ld",&n);
	ciur(n);
	printf("%ld\n",v[0]);
	fclose(stdin);
	fclose(stdout);
	return 0;
}