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

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

const int NMAX = 1e6;

int n;
int phi[NMAX + 2];

long long ans;

int main()
{
    in >> n;

    for(int i = 1; i <= n; i++)
        phi[i] = i - 1;

    for(int i = 1; i <= n; i++)
        for(int j = 2 * i; j <= n; j += i)
            phi[j] -= phi[i];

    ans = 1;
    for(int i = 1; i <= n; i++)
        ans += 2LL * phi[i];

    out << ans << '\n';

    return 0;
}