#include <bits/stdc++.h>

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
const int N = 1000001;
int n,phi[N],sol=1;
int main()
{
    f>>n;
    for(int i=1;i<=n;i++)
        phi[i]=i;
    /// se calculeaza phi[i] pentru orice i de la 2 la n;
    for(int i=2;i<=n;i++)
    {
        if(phi[i]==i)///daca i este prim
            for(int j=i;j<=n;j+=i)
                phi[i]=phi[i]/i*(i-1);
        sol+=2*phi[i];
    }
    g<<sol<<'\n';
    return 0;
}

1 2 3 4 ... N
1 1 2 2 ->5*2=10+1
1+2*(phi(2)+phi(3)+phi(4))

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1 1 2 2 4 2 6 4 6  5 10  6 12  7 10  8 16  9
                   4     4     6  8        6
1 2  4 5  7 8

 x*3^a ->x*2*3^(a-1)