#include <bits/stdc++.h>
#define Nmax 1000000
using namespace std;
int ciur[Nmax], n;
void phi()
{
    int i, j;
    for(i = 1; i <= n; ++i)
    {
        ciur[i] = i;
    }
        for(i = 2; i <= n; ++i)
        {
            if(ciur[i] == i)
            {
                for(j = i; j <= n; j+=i)
                {
                    ciur[j] = ciur[j] * (i - 1) / i;
                }
            }
        }
}
ifstream f("fractii.in");
ofstream g("fractii.out");
int main()
{
    f >> n;
    phi();
    unsigned long long s = 0;
    for(int a = 2; a <= n; ++a)
    {
        s = s + 2 * ciur[a];
    }
    s = s + 1;
    g << s;
    return 0;
}