#include<fstream>
#include<iostream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int j,n,i;
long long v[1000010],s;
int main ()
{
    in>>n;
    for(i=2;i<=n;i++)
        v[i]=i;

    for(i=2;i<=n;i++)
        if(v[i]==i)
            for(j=i;j<=n;j=i+j)
                v[j]=v[j]/i*(i-1);


    for(i=2;i<=n;i++)
            s=s+v[i];
    out<<s*2+1;
    in.close();
    out.close();
    return 0;
}