#include <iostream>
#include <fstream>
using namespace std;
ifstream  f("fractii.in");
ofstream  g ("fractii.out");

    long long i, j, N, s = 0;
    long long  phi[1000000];

int main(){

    f >> N;


    for (i = 2; i <= N; ++i)
        phi[i] = i;
        for (i=2;i<=N;i++)
            if (phi[i]==i)
                for (j=i;j<=N;j+=i){
                    phi[j] /=i;
                    phi[j] *= (i-1);
                }

    for (i = 1; i <= N; i++)
        s+=phi[i];
    g << s*2+1;
    f.close();
    g.close();

return 0;
}