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

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
ll n, ans;
ll phi[1000009];
bitset <1000009> v;
void chiur()
{
    for(ll i = 1; i <= n; ++i)
        phi[i] = i;

    for(ll i  = 2; i <= n; ++i)
        if(v[i] == 0)
        {
            for(int j = i ; j <= n; j +=i)
            {
                phi[j] /= i;
                phi[j] *= i - 1;
                v[j] = 1;
            }
        }
}
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;
}