#include <fstream>
#include <vector>
#include <math.h>

//http://www.infoarena.ro/problema/fractii

const char* inFile = "fractii.in";
const char* outFile = "fractii.out";




std::vector<bool> init_primes_sieve(int n)
{
    std::vector<bool> sieve(n + 1, true);

    auto max_prime_check = int(sqrt(n));

    for (int p = 2; p <= max_prime_check; ++p)
    {
        if (!sieve[p]) continue;

        auto multiple_p = 2 * p;

        while (multiple_p <= n)
        {
            sieve[multiple_p] = false;
            multiple_p += p;
        }
    }
    return sieve;
}

unsigned long long get_sum_totients(int n, const std::vector<bool>& sieve)
{

    std::vector<int> primes;

    for (int i = 2; i <= n; ++i)
    {
        if (sieve[i])
        {
            primes.push_back(i);
        }
    }

    std::vector<int> cached_totients(n + 1, 0);
    for (auto k = 2; k <= n; ++k)
    {
        if (sieve[k])
        {
            cached_totients[k] = k - 1;
            continue;
        }

        for (auto p : primes)
        {
            if (p > sqrt(k)) continue;

            if (k % p == 0)
            {
                auto l = k / p;
                auto tot_l = cached_totients[l];
                if (l % p == 0)
                {
                    tot_l *= p;
                }
                else
                {
                    tot_l *= p - 1;
                }

                cached_totients[k] = tot_l;
                break;
            }
        }
    }

    unsigned long long sum = 0;
    for (auto t : cached_totients)
    {
        sum += t;
    }

    return sum;
}


unsigned long long compute_num_irred_fractions(int n)
{
    if (n == 1) return 1;
    auto sieve = init_primes_sieve(n);

    auto sum_totients = get_sum_totients(n, sieve);

    return 1 + 2 * sum_totients;
}


int main()
{
    int n = 0;
    {
        std::ifstream readFile(inFile);
        if (!readFile) return -1;

        readFile >> n;
    }

    auto num = compute_num_irred_fractions(n);
    {
        std::ofstream writeFile(outFile);
        writeFile << num;
    }

    return 0;
}