#include <bits/stdc++.h>

using namespace std;
const int N = 1e6 + 5;
vector <int> primes;
int euler[N];
void ciur(int n)
{
    fill(euler + 2, euler + n + 1, 1);
    for(int i = 2; i <= n; i++) {
        if(euler[i] == 1) euler[i] = i - 1, primes.push_back(i);
        for(int j = 0; j < primes.size() && i * primes[j] <= n; j++) {
            euler[i * primes[j]] = euler[i] * (primes[j] - !!(i % primes[j]));
            if(i % primes[j] == 0) break;
        }
    }
}

int main()
{
    ifstream cin("fractii.in");
    ofstream cout("fractii.out");
    int n;
    cin >> n;
    ciur(n);
    for(int i = 2; i <= n; i++)
        euler[i] *= 2;
    cout << accumulate(euler + 2, euler + n + 1, 0ll) + 1;
    return 0;
}