#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;

ifstream in("fractii.in");
ofstream out("fractii.out");

long long v[1000001],g1[1000001],g2[1000001],stot,n;

int main()
{
    in>>n;
    v[0]=v[1]=-1;
    for(int i=2;i<=n;i++) if(v[i]==0) for(int j=1;i*j<=n;j++){
            if(g1[i*j]==0)g1[i*j]=i-1;
            else g1[i*j]*=i-1;
            if(g2[i*j]==0)g2[i*j]=i;
            else g2[i*j]*=i;
            if(j!=1)v[i*j]=1;
    }
    for(int i=2;i<=n;i++) stot+=i*g1[i]/g2[i];
    out<<stot*2+1;
}