#include <fstream>

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

long long n, m, i, j, ans;
int prime[1000001];

int main()
{
    f >> n;
    // indicatorul Euler
    for(i = 2; i <= n; i ++)
        prime[i] = i - 1;
    for(i = 2; i <= n; i ++)
    {
        ans += prime[i];
        for(j = i * 2; j <= n; j += i)
            prime[j] = prime[j] - prime[i];
    }
    g << 2 * ans + 1;
    f.close();
    g.close();
    return 0;
}