#include <fstream>

using namespace std;
int const N = 1e6 + 1;
int v [N];
ifstream f ("fractii.in");
ofstream g ("fractii.out");
int main()
{
    int n;
    f >> n;
    v [1] = 1;
    for(int i = 2 ; i <= n ; ++ i)
        v [i] = i - 1;
    for(int i = 2 ; i <= n ; ++ i)
        for(int j = 2 * i ; j <= n ; j += i)
            v [j] -= v [i];
    long long ans = v [1];
    for(int i = 2 ; i <= n ; ++ i)
        ans = ans + 2LL * v [i];
    g << ans;
    return 0;
}