#include <fstream>
#include <bitset>

using namespace std;

ifstream fin ("ciur.in");
ofstream fout ("ciur.out");

int n,i,j,nr;
bitset <2000005> a;
int main()
{
    fin>>n;
    for(i=4;i<=n;i+=2)
        a[i]=1;
    for(i=3;i*i<=n;i+=2)
        if(!a[i])for(j=i*i;j<=n;j=j+2*i)a[j]=1;
    //for(i=1;i<=n;i+=2)if(!a[i])++nr;
    fout<<n-a.count()-1;
    //for(i=1;i<=n;++i)fout<<a[i]<<' ';

    fin.close(); fout.close();
    return 0;
}