#include <cstdio>
#include <fstream>
#define nmax 1000005
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n,sol;
int v[nmax];


int main()
{
    int i,j;
    f>>n;
    sol=1;
    for (i=2; i<=n; i++) v[i]=i-1;

    for (i=2; i<=n; i++)
    {

        for (j=2*i; j<=n; j+=i)

            v[j]-=v[i];

        sol+=v[i]<<1;
    }
    g<<sol;

    return 0;
}