#include <fstream>
typedef unsigned long long lunguet;
using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int n, v[1000002];
lunguet sumavector;
lunguet calculeaza(lunguet n){
    for (int i=2; i<=n; i++) v[i]=i-1;
    for (int i=2; i<=n; i++)
    {
        sumavector+=v[i];
        for (int j=i+i; j<=n; j+=i) v[j]-=v[i];
    }
    return sumavector*2+1;
}

int main()
{
    f>>n;
    g<<calculeaza(n);
    return 0;

}