#include <fstream>

using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int n, phi[1000001];
long long ans;
int main()
{
    cin >> n;
    for(int i; i<=n; i++)
        phi[i] = i;
    for(int i=2; i<=n; i++)
        if(phi[i] == i)
            for (int j = i; j <= n; j += i)
                phi[j] -= phi[j] / i * (i - 1);
    for(int i=1; i<=n; i++)
        ans += phi[i] * 2;
    cout << ans - 1;
    return 0;
}