#include <iostream>
#include <bits/stdc++.h>

using namespace std;

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

int v[1000010];
long long int nr = 0;

int Fractii(int n)
{
    for (int i = 2; i <= n; i++)
        v[i] = i-1;
    for (int i = 2; i <= n; i++)
        for (int j = 2*i; j <= n; j = j+i)
            v[j] -= v[i];
    for (int i = 2; i <= n; i++)
        nr += v[i]*2;
    return (nr+1);

}

int main()
{
    int n;
    fin >> n;
    fout << Fractii(n);
    return 0;
}