# include <bits/stdc++.h>

using namespace std;

const int Nmax = 1000000 + 5;

int N, a[Nmax];
long long nr = 1LL;

int main ()

{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);

    scanf("%d", &N);

    for (int i = 1; i <= N; ++i) a[i] = i - 1;

    for (int i = 1; i <= N; ++i) {

        nr += 1LL * a[i];

        for (int j = 2 * i; j <= N; j += i) a[j] -= a[i];

    }

    nr = nr * 2;

    printf("%lld\n", --nr);

    return 0;
}