#include<stdio.h>
#define NMAX 2002001
#define MMAX 2001
char x[NMAX];
long k,rez[MMAX],i,n,j ;
int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%ld",&n);
	k=n;
	for (i=2;i<=n;i++)
		if (x[i]==0)
		{
			for (j=i+i;j<=n;j+=i)
				x[j]=1;
			k--;

		}
	for (i=n;i>=2&&rez[0]<1000;i--)
		if (x[i]==0)
			rez[++rez[0]]=i;
	printf("%ld\n",n-k);
/*	for (i=rez[0];i>=1;i--)
		printf("%ld ",rez[i]);
	printf("\n");*/



	return 0;
}