#include <fstream>
using namespace std;

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

int phi[1000001];

int main()
{
    int N; unsigned long long count = 0; in >> 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 = 2; i <= N; i++)
        count += (unsigned long long)2*phi[i];
    out << count+1;
    return 0;
}