#include <cstdio>
#include <cstdlib>
using namespace std;

const int NMAX = 1000010;

int N, Phi[NMAX];
long long Ans;

int main()
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);

    scanf("%i", &N);

    for(int i = 2; i <= N; ++ i)
        Phi[i] = i - 1;
    for(int i = 2; i <= N; ++ i)
    {
        Ans += 2LL * Phi[i];
        for(int j = 2 * i; j <= N; j += i)
            Phi[j] -= Phi[i];
    }
    printf("%lld\n", Ans + 1);
}