#include<iostream>
#include<fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int phi(int n)
{
    int r = n , d = 2;
    while(n > 1)
    {
        if(n % d == 0)
        {
            r = r / d * (d - 1);
            while(n % d == 0)
                n /= d;
        }
        d ++;
        if(d * d > n)
            d = n;
    }
    return r;
}
int main()
{
    long long n;
    f >> n;
    long long c=1,i=2;
    while(i<=n)
    {
        c=c+2*phi(i);
        i++;
    }
    g<<c;
}