#include <iostream>
#include <fstream>
using namespace std;

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

long nr = 1, n, v[1000000];

int main()
{
    f>>n;
    for(int i = 2; i <= n; i ++) v[i] = i;

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

    for(int i = 1; i <= n; i ++)
    {
        if(v[i] == i)
            nr += (v[i]-1) * 2;
        else
            nr += v[i] * 2;
    }
    g<<nr;

    return 0;
}