#include <cstdio>


using namespace std;
int i,a[2000009],nr,n,j;
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);

   scanf("%d",&n);

    for(i=1; ((i*i ) <<1) + (i<<1) <=n ; ++i)
      if((a[i>>3] & (1<< (i & 7))) ==0)
    for(j=((i * i) <<1 ) +(i<<1); (j<<1)+1<=n ;j+=(i<<1) )
      a[i>>3]|=(1<<(j & 7));

    nr=0;
    for(i=1;(i<<1)+1<=n;++i)
     if((a[i<<3] & (1<<(i&7)))==0) ++nr;



    printf("%d\n",nr);

    return 0;
}