#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N;
    cin >> N;
    vector<ll> tb(N + 1);
    ll ans = 0;
    for(int i = N; i >= 2; i--){
        ll c = N / i;
        tb[i] = c * (c - 1) / 2;
        for(int j = 2 * i; j <= N; j += i) tb[i] -= tb[j];
        ans += tb[i] - (c - 1);
    }
    cout << ans << '\n';
}