#include <cstdio>
#define MAX 2000001
int ciur[MAX];
int cnt,n,j;
int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%d",&n);
	for(int i = 2;i <= n;i++)
	{
		if(ciur[i] == 0)
		{
			j = i;
			while(j++ < n)
			{	
				if(j % i == 0) 
					ciur[j] = 1;
				else if(ciur[j] != 1)
					ciur[j] = 0;
			}
			cnt++;
		}
	}
	printf("%d ",cnt);
	return 0;
}