#include<fstream>

using namespace std;
long long i,j,N,total;
int phi[1000005];

int main()
{
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    fin>>N;

    for(i=1;i<=N;i++)
       phi[i]=i;
    for(i=1;i<=N;i++)
    {

        for(j=i+i;j<=N;j+=i)

            phi[j]-=phi[i];
    }
    for(i=1;i<=N;i++)
       total+=phi[i];
    total=total*2-1;
    fout<<total;
    return 0;
}