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

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

int main()
{
    int n;
    fin >> n;

    vector<int> phi(n + 1);
    for (int i = 0; i <= n; i++)
        phi[i] = i;

    for (int i = 2; i <= n; i++)
        if (phi[i] == i)                 // i este prim
            for (int j = i; j <= n; j += i)
                phi[j] -= phi[j] / i;

    long long ans = 1;                   // fracția 1/1
    for (int k = 2; k <= n; k++)
        ans += 2LL * phi[k];

    fout << ans << "\n";
    return 0;
}