#include <iostream>
#include <fstream>
using namespace std;
# define max 1000001
int v[max];

int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    long long int n, i, j, nr = 1;
    f>>n;
    for(i = 1; i <= n; i++)
        v[i] = i - 1;
    for(i = 2; i <= n; i++)
    {
        nr += 2 * v[i];
        for(j = 2 * i; j <= n; j += i)
            v[j] -= v[i];
    }
    g<<nr;
    f.close();
    g.close();
    return 0;
}