#include <fstream>

using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int v[1000002];
int main()
{
    int n;
    in>>n;
    int i,j;
    long long sum=1;
    /// implementarea logica a formulei matematice
    for(i=2; i<=n; i++)
    {
        v[i]+=i-1;
        /// prin for eliminam numerele puse in plus (mai degraba multipli)
        for(j=i*2; j<=n; j+=i)
            v[j] -= v[i];
        sum+=(v[i]*2);
    }
    out<<sum;
    return 0;
}