#include <fstream>
using namespace std;
ifstream in ("fractii.in");
ofstream out ("fractii.out");
int e[1000001];

int main()
{
    long long n, i, j, k, s=1;
    in >> n;
    for ( i=1; i<=n; i++)
    {
        for (i=1; i<=n; i++)
            e[i]=i;
        for (i=2; i<=n; i++)
            if ( e[i] == i)
                for (j=i; j<=n; j+=i)
                {
                    e[j]=e[j]/i*(i-1);

                }
    }
    for ( i=2; i<=n; i++)
    {
        s+=2*e[i];
    }
    out << s;
    return 0;
}