#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int phi[1000001];
int main()
{
    int n,k=1;
    f >> n;
    for (int i = 1; i <= n; ++i)
        phi[i] = i-1;
    for (int i = 2; i <= n; ++i)
        for (int j = 2*i; j <=n; j += i)
            phi[j] -= phi[i];
    for(int i=1; i<=n; i++)
       k+=phi[i]*2;
    g << k;
    return 0;
}