#include <bits/stdc++.h>

using namespace std;

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

const int dim = 1000010;

long long n, phi[dim];

void euler()
{
    for(long long i = 2;i <= n;i++)
        phi[i] = i;
    phi[1] = 0;
    for(long long i = 2;i <= n;i++)
    {
        if(phi[i] == i)
        {
            for(long long j = i;j <= n;j += i)
            {
                phi[j] /= i;
                phi[j] *= i - 1;
            }
        }
    }
}

int main()
{
    in>>n;
    euler();
    long long rez = 1;
    for(long long i = 2;i <= n;i++)
        rez += 2 * phi[i];
    out<<rez;
    return 0;
}