#include <fstream>

using namespace std;
ifstream in ("ciur.in");
ofstream out ("ciur.out");
const int NMAX=2000000/16+1;
char ciur[NMAX];
int main()
{
    int n;
    in>>n;
    int i,j;
    for(i=1;((i*i)<<1)+(i<<1)<=n;i++)
    {
        if((ciur[i>>3]&(1<<(i&7)))==0)
        {
            for(j=((i*i)<<1)+(i<<1);(j<<1)+1<=n;j+=(i<<1)+1)
            ciur[j>>3]|=(1<<(j&7));
        }
    }
    int cnt=1;
    for(i=1;2*i+1<=n;i++)
    {
        if((ciur[i>>3]&(1<<(i&7)))==0)
        cnt++;
    }
    out<<cnt;
    return 0;
}