#include<fstream>
#define DM 1000007
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");

long long Sol;
int N;
int F[DM];

int main()
{
    fin>>N;

    for(int i=2;i<=N;++i)
        F[i]=i;

    for(int i=2;i<=N;++i)
    {
        for(int j=1;j*i<=N;++j)
            F[j*i]--;
    }

    for(int i=2;i<=N;++i)
        Sol+=F[i];

    Sol*=2;
    Sol++;

    fout<<Sol<<"\n";

    fin.close();
    fout.close();
    return 0;
}