#include <iostream>
#include <fstream>
#define NMax 1000005
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n,i,j,v[NMax];
unsigned long long rez;
int main()
{
    f>>n;
    for (i=2;i<=n;i++) v[i]=i-1;
    for (i=2;i<=n;i++)
    {
        rez=rez+v[i];
        for (j=i+i;j<=n;j=j+i)
            v[j]=v[j]-v[i];
    }
    g<<1LL*(rez*2+1);
}