#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;
unsigned v[1000001], n, s=0;
ifstream f("fractii.in");
ofstream g("fractii.out");
int main ()
{

    f>>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+=i)
        {
            v[j]-=v[i];
        }
    }
    for(int i=2;i<=n;i++)
    {
        s+=2*v[i];
    }
    g<<s-1;
    return 0;
}