#include <fstream>
#define nmax 1000005
using namespace std;
int n,nr[nmax];
long long int sol = 1;

int main()
{
    ifstream in("fractii.in");
    ofstream out("fractii.out");
    in>>n;
    int i,j;
    for(i=1;i<=n;i++)
        nr[i]=i-1;
    for(i=2;i<=n;i++)
    {sol+=nr[i]*2;
    for(j=i*2;j<=n;j=j+i)
        nr[j]-=nr[i];
    }

    out<<sol<<'\n';
    return 0;
}