#include <iostream>
#include <fstream>
using namespace std;
int n,i,k,t,p,s,ok;
int main()
{
    ifstream fin ("fractii.in");
    ofstream fout ("fractii.out");
    fin>>n;
    for(i=1;i<=n;i++)
    {
        t=i;k=2;p=i;
        while(t!=1)
        {
            ok=0;
            while(t%k==0){t/=k;ok=1;}
            if(ok)
            {
                p*=(k-1);
                p/=k;
            }
            k++;
        }
        s+=p*2;
    }
    fout<<s-1;
    return 0;
}