#include <fstream>
using namespace std;
short v[1001];
int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    int n,k,i,j,c=1,x;
    f>>n;
    k=2*n-1;
    if (n<3) g<<k<<'\n';
    else
    {
        for (i=2;i*i<=n;i++)
        {
            for (j=2;i*j<=n;j++)
                v[i*j]=1;
        }
        for (i=2;i<=n;i++)
            if (v[i]!=1)
            {
                x=i;
                k+=2*(n-(c+n/x))+1;
                c++;
            }
        g<<k<<'\n';
    }
    f.close();
    g.close();
    return 0;

}