#include <fstream>

using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int v[10000001];
int main()
{
    int n,i,j;
    long long sol=0;
    in >> n;
    for (i = 2; i <= n; i++)
    {
        v[i] = i - 1;
    }
    for (i = 2; i <= n; i++)
    {
        sol += v[i];
        for (j = i*2; j <= n; j += i)
        {
            v[j] -= v[i];
        }
    }
    out<<sol*2+1;
    return 0;
}