#include<stdio.h>
#define DIM 200001 
int n,i,j,prim,k,a[DIM];
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);

	scanf("%d", &n);

	for(i=2;i<=n;++i)
	{
                     k=0;
                     j=2;
			while(j<i)
			{
                       if(i%j==0)
                       ++k;
                       ++j;
            }
            if(k==0)
            ++prim;
   }
   printf("%d",prim);
   return 0;
}