#include <fstream>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
int main()
{
    int n,s=0,gasit;
    char nr[2000001];
    f>>n;
    for(int i=3;i<=n;i+=2)nr[i]=0;
    for(int i=3;i<=n;i+=2)
        for(int j=i*i;j<=n;j+=2*i)
        {
            {if(nr[j]!=1)s++;
            nr[j]=1;}
        }
    g<<n-(n/2)-s;
    f.close();
    g.close();
}