#include <fstream>
using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n;
int v[1000001];
long long s;
int main()
{
    fin >> n;
    s = 1;
    for (int i = 1; i <= n; i++){
        v[i] = i;
    }
    for (int i = 1; i <= n; i++){
        for (int j = i * 2; j <= n; j = j + i){
            v[j] = v[j] - v[i];
        }
    }
    for (int i = 2; i <= n; i++){
        s = s + 2 * v[i];
    }
    fout << s;
}