#include <fstream>

using namespace std;
int a[1000001], n;
void Phi (int n)
{
    int i, j;
    for (i=2; i<=n; i++)
        a[i]=i-1;
    for (i=2; i<=n; i++)
        for (j=i+i; j<=n; j=j+i)
            a[j]=a[j]-a[i];
}
int main()
{
    ifstream fin ("fractii.in");
    ofstream fout ("fractii.out");
    int i;
    long long s;
    Phi(1000000);
    s=1;
    fin >> n;
    for (i=2; i<=n; i++)
        s=s+2*a[i];
    fout << s << "\n";
    fin.close ();
    fout.close();
    return 0;
}