#include <fstream>
//#include <iostream>
using namespace std;

int euler[1000001];

int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    int N;
    long long sum=1;
    f>>N;
    for (int i=2;i<=N;i++)
        euler[i]=i-1;
    for (int i=2;i<=N;i++)
    {
        for (int j=2*i;j<=N;j+=i)
            euler[j]-=euler[i];
        sum+=euler[i];
    }
    g<<2*sum-1;
    f.close();
    g.close();
}