#include <bits/stdc++.h>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
const int N = 1e6+5;
int phi[N];
int main()
{
    int n;
    long long s=0;
    in >> n;
    for (int i = 1; i<=n; i++)
        phi[i] = i;
    for (int i = 1; i<=n; i++)
    {
        for (int j = 2*i; j<=n; j+=i)
            phi[j]-=phi[i];
        s+=phi[i];
    }
    out << 2ll*s-1;
}