#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
const ll MOD1000000007 = 1000000007;
const ll MOD998244353 = 998244353;
const ll MOD[3] = {999727999, 1070777777, 1000000007};
const ll LINF = 1LL << 60LL;
const int IINF = (1 << 30) - 1;


void solve(){
    ll n; cin >> n;

    ll ans0 = 0;
    for(ll i=2; i<=n; i++){
        for(ll j=2*i; j<=n; j+=i){
            ans0++;
        }
    }
    
    vector<ll> dp(n+1, 0);
    for(ll i=n; i>=1; i--){
        ll cnt = 1;
        for(ll j=2*i; j<=n; j+=i){
            cnt++;
            dp[i] -= dp[j];
        }
        dp[i] += cnt*(cnt-1)/2;
    }

    ll ans = n*(n-1)/2 - dp[1] - ans0;
    cout << ans << endl;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    int T=1;
    //cin >> T;
    while(T--) solve();
}