#include<fstream>
using namespace std;
#define INPUTFILE "fractii.in"
#define OUTPUTFILE "fractii.out"
#define DIM 1000001
ifstream fin (INPUTFILE);
ofstream fout (OUTPUTFILE);
long long a[DIM];
int main ()
{
    long long i,j,n,S=0;
    fin>>n;
    for (i=2; i<=n; ++i)
    {
        if (!a[i])
        {
                  S+=i-1;
        for (j=2*i; j<=n; j+=i)
            if(!a[j])
                  a[j]=j-j/i;
            else
                  a[j]-=a[j]/i;
        }
        else
            S+=a[i];   
    }
    S=S*2+1;
    fout<<S;
    return 0;
}