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

int n, v[1000001];
long long fractii = 1;

int main() {
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    cin >> n;

    for(int i = 1; i <= 1000000; i++)
        v[i] = i-1;
    for(int i = 2; i <= 1000000; i++)
        for(int j = 2*i; j <= n; j+= i)
            v[j] -= v[i];

    for(int i = 2; i <= n; i++)
        fractii += 2 * v[i];

    cout << fractii;
    f.close();
    g.close();
    return 0;
}