#include<iostream>
#include<stdio.h>
using namespace std;
int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	int v[100],i,j,x,n,nr=0;
	scanf("%d",&n);
	for(i=1;i<=n-1;i++)
		v[i]=i+1;
	for(i=1;i<=n-1;i++)
		if(v[i]!=0)
		{
			x=v[i];
			for(j=i+x;j<=n-1;j+=x)
				v[j]=0;
		}
	for(i=1;i<=n-1;i++)
		if(v[i]!=0)
			nr++;
	printf("%d",nr);
	return 0;
}