#include <bits/stdc++.h>
using namespace std;

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

int n;
long long nr = 1;

int Phi(int x)
{
    int prod = 1, d = 2;
    while(x > 1)
    {
        int p = 0, tmp = 1;
        while(x % d == 0)
        {
            ++p;
            x /= d;
            tmp *= d;
        }
        if (p) prod *= (d - 1) * tmp / d;
        ++d;
        if (x > 1 && d * d > x) d = x;
    }
    return prod;
}

int main()
{
    fin >> n;

    for (int i = n; i > 1; --i)
    {
        int tmp = Phi(i);
        nr += 2LL * tmp;
    }

    fout << nr;
    fin.close();
    fout.close();
    return 0;
}