#include <iostream>
#include <fstream>
using namespace std;
int a[1000001],n;
void Phi(int n)
{   int i,j;
    for(i=2;i<=n;i++)
        a[i]=i-1;
    for(i=2;i<=n;i++)
        for(j=i+i;j<=n;j=j+i)
            a[j]=a[j]-a[i];



}
int main()
{
    int i;long long S;
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    Phi(1000000);
    fin>>n;
    S=1;
    for(i=2;i<=n;i++)
        S=S+2*a[i];

    fout<<S;

        fin.close();
        fout.close();



        return 0;

}