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

int main()
{
    ifstream g("fractii.in");
    ofstream h("fractii.out");
    g>>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];
    }

    h<<sol<<endl;
    g.close();
    h.close();
    return 0;
}