# include<fstream>
# include<bits/stdc++.h>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int N,m=1,a[1000001];
int main()
{
	fin>>N;
   for (int i=1 ; i<N;i++)
   	a[i+1]=i;
    for (int i =2; i <= N; i++)
    {
        m +=a[i]*2;
        for (int j=i*2;j<=N;j+=i)
        {
            a[j]-=a[i];
        }
    }
    fout<<m;	
}