#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)+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+1);

    return 0;
}