#include<fstream>
#include<vector>
using namespace std;
long N;
long long P,Q;

long phi[1000000];

int main()
{
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    fin>>N;
    long long total=0;
    for(P=2;P<=N;P++)
    phi[P]=P-1;
    for(P=2;P<=N;P++)
    {
        total+=phi[P];
        for(Q=P*2;Q<=N;Q+=P)
            phi[Q]-=phi[P];
    }
    total=total*2+1;
    fout<<total;
    return 0;
}