#include <bits/stdc++.h>
#define ll long long

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
ll n, ans;
vector <ll> ceva[1000009];
bitset <1000009> v;
ll Phi(ll n)
{
    ll sol = n;
    for(int i = 0; i < ceva[n].size(); ++i)
    {
        sol /= ceva[n][i];
        sol *= ceva[n][i] - 1;
    }
    //g << n << ' ' << sol << '\n';
    return sol;
}
void chiur()
{
    for(ll i  = 2; i <= n; ++i)
        if(v[i] == 0)
        {
            for(int j = i ; j <= n; j +=i)
            {
                v[j] = 1;
                ceva[j].push_back(i);
            }
        }
}
int main()
{
    f >> n;
    chiur();
    for(ll i = 2; i <= n; ++i)
        ans += 2 * Phi(i);
    ans++;
    g << ans;
    f.close();
    g.close();
    return 0;
}