#include <fstream>

using namespace std;

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

int v[1000001];

int main()
{
    int n;
    unsigned long long nr = 0;
    fin >> n;
    fin.close();
    for(int i = 2; i <= n; ++i) v[i] = i - 1;
    for(int i = 2; 2 * i <= n; ++i)
        for(int j = 2 * i; j <= n; j += i) v[j] -= v[i];
    for(int i = 2; i <= n; ++i) nr += 1LL * v[i];
    fout << nr * 2 + 1;
    fout.close();
    return 0;
}