#include <iostream>
#include <fstream>
#include <math.h>

using namespace std;

ifstream in("fractii.in");
ofstream out("fractii.out");

int n;
int pr[78500];

void prime()
{
    char a[1000000] = {0};

    int cnt = 1;
    int p = sqrt(n)+1;
    pr[0] = 2;
    for ( int i = 3; i <= n; i += 2 )
    {
        if ( a[i] == 0 )
        {
            pr[cnt++] = i;
            if ( i <= p )
            {
                for ( int j = (i<<1); j <= n; j += i )
                    a[j] = 1;
            }
        }
    }
}

int totv[1000000] = {0, 1, 1, 2, 2}; // totv[i] = tot(i)

int tot(int x)
{
    int p = x;

    int i = 0;
    int cnt = 0;
    int gasit = 0;

    if ( totv[x] != 0 )
       return totv[x];

    while ( pr[i] < p )
    {
        if ( p % pr[i] == 0 )
        {
            gasit = 1;
            break;
        }
        ++i;
    }

    if ( !gasit )
    {
        totv[x] = x-1;
        return totv[x];
    }

    while ( p % pr[i] == 0 )
    {
        p /= pr[i];
        ++cnt;
    }

    // p = 3, cnt = 1

    if ( p == 1 )
        //totv[x] = (pr[i]-1)*pow(pr[i], cnt-1);
        totv[x] = (pr[i]-1)*(x/pr[i]);
    else
    {
        int g = pow(pr[i], cnt-1);
        //totv[x] = (pr[i]-1)*pow(pr[i], cnt-1)*totv[x / (int)pow(pr[i], cnt)];
        totv[x] = (pr[i]-1)*g*totv[x / (g*pr[i])];
    }

    return totv[x];
}

int main()
{
    in >> n;
    prime();

    long long sol = 0;

    //cout << tot(n) << endl;

    for ( int j = 2; j <= n; ++j )
        sol += tot(j);

    sol = sol*2 + 1;

    out << sol << endl;

	return 0;
}