#include <fstream>
using namespace std;
ifstream fin ("ciur.in");
ofstream fout ("ciur.out");
int N,v[2000010],i,x,j;
int main()
{
    fin >> N;
    for(i=2;i<=N;i++)
    {
        if(v[i]!=1)
           x++;
        for (j=i;j<=N;j=j+i)
            {
                if(v[j]%v[i]==0)
                    v[j]=1;
            }
    }
    fout << x;
    return 0;
}