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

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int main()
{
    int n;
    fin >> n;

    int tot[n];
    for (int i=1; i<=n; i++) {
        tot[i] = i;
    }

    for (int i=2; i<=n; i++) {
        if (tot[i] == i) {
            tot[i] -= 1;  // phi(i) = i-1 daca i prim
            for (int j=2; i*j <= n; j++) {
                tot[i*j] = tot[i*j]/i * (i-1);
            }
        }
    }

    /*
    for (int i = 1; i<=n; i++) {
        cout << tot[i] << " ";
    }
    */

    long long sol = 0;
    for (int i=2; i<=n; i++) {
        sol += tot[i];
    }
    sol = 2*sol + 1;
    cout << sol;

    return 0;
}