#include <iostream>
#include <fstream>

using namespace std;

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

const int N = 1000000 + 5;

long long int n, sum;
long long int pi[N];

int main()
{
    fin >> n;

    for (int i = 1; i <= n; i++)
        pi[i] = i;
    for (int i = 2; i <= n; i++)
        if (pi[i] == i)
            for (int j = i; j <= n; j += i)
            {
                pi[j] /= i;
                pi[j] *= (i - 1);
            }

    for (int i = 2; i <= n; i++)
        sum += pi[i];
    fout << 2 * sum + 1;

    return 0;
}