#include <iostream>
#include <fstream>

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");

int main()
{
    long long int n = 0, V[1000000];
    f >> n;
    for (int i = 1; i <= n; i++) {
        V[i] = i;
    }
    for (int i = 2; i <= n ; i++) {
        V[i]--;
        for (int j = 2 * i; j <= n; j += i) {
            V[j] -= V[i];
        }
    }
    long long int contor = 0;
    for (int i = 1; i <= n; i++) {
        contor += V[i] * 2;
    }
    g << contor - 1;
    return 0;
}