#include <fstream>
#define nMax 1000005
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int n, phi[nMax];

int main()
{
    in >> n;
    for(int i = 1; i <= n; ++i)
        phi[i] = i-1;
    for(int i = 2; i <= n; ++i)
        for(int j = (i<<1); j <= n; j += i)
            phi[j] -= phi[i];
    long long nr = 1;
    for(int i = 2; i <= n; ++i)
        nr += (phi[i]<<1);
    out << nr << '\n';
    in.close(), out.close();
    return 0;
}