#include <cstdio>
#include <cmath>

long long SUM;
int N;
int primes[1000001];
int p[100000];
int nr_primes;

int fi(int n)
{
    if (primes[n] == 0)
    {
        return n - 1;
    }
    int result = n;
    for(int i = 0; p[i] * p[i] <= n; i++)
    {
        if (n % p[i] == 0) result -= result / p[i];
        while (n % p[i] == 0) n /= p[i];
    }
    if (n > 1) result -= result / n;
    return result;
}

void check_primes()
{
    p[nr_primes] = 2;
    nr_primes++;

    for(int i = 4; i <= N; i+=2)
    {
        primes[i] = 1;
    }

    for(int i = 3; i <= N; i+=2)
    {
        if(primes[i] == 0)
        {
            p[nr_primes] = i;
            nr_primes++;

            for(int j = 2*i; j <= N; j+=i)
            {
                primes[j] = 1;
            }
        }
    }
}

int main()
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    scanf("%d", &N);
    check_primes();

    for (int i = 2; i <= N; i++)
    {
        SUM += fi(i);
    }

    SUM = 2 * SUM + 1;

    printf("%lld\n", SUM);
    return 0;
}