#include<stdio.h>
using namespace std;


unsigned phi(unsigned long x)
{
    unsigned ret = 1,i,pow;

    for (i = 2; x != 1; i++)
    {
        pow = 1;
        while (!(x%i))
        {
            x /= i;
            pow *= i;
        }
            ret *= (pow - (pow/i));
    }
    return ret;
}

int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
	long int n,i,z=1;
	scanf("%lu",&n);
	for(i=2;i<=n;i++)
        z=z+phi(i)*2;
    printf("%u",z);
    return 0;
}