#include <iostream>
#include <fstream>
using namespace std;
const int nmax=1000000;
int phi[nmax];
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int main()
{
    int N,nr=0,j,cx=0;
    fin>>N;
    for(int i=2;i<=N;i++)
        phi[i]=i-1;
    for(int i=2;i<=N;i++)
    {
        nr=nr+phi[i];
        for( j=2*i;j<=N;j=j+i)
        phi[j]=phi[j]-phi[i];
    }

    fout<<nr*2+1  <<"\n";
    return 0;
}