#include <iostream>
#include <fstream>
#define NMAX 1000001

using namespace std;

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


int phi[NMAX];
int n;

int main()
{
    fin >> n;
    long long s = 0;
    for (int i=1;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;
            phi[j] = phi[j] * (i-1);
        }
    }
    for (int i=2;i<=n;++i)
        s+=phi[i];
    fout << 1 + 2 * s;

    return 0;
}