#include <fstream>
#define NMAX 1000005
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n, a[NMAX];
long long int nr = 1;
int main()
{   fin>>n;
    int i,j;
    for(i=1;i<=n;i++)
        a[i]=i-1;
    for(i=2;i<=n;i++)
       {nr+=a[i]*2;
        for(j=i*2;j<=n;j=j+i)
            a[j]-=a[i];
       }
    fout<<nr<<endl;
}