#include "bits/stdc++.h"
using namespace std;
 
#define ll long long
 
#define       forn(i,n)              for(int i=0;i<n;i++)
#define          all(v)              v.begin(), v.end()
#define         rall(v)              v.rbegin(),v.rend()
 
#define            pb                push_back
#define          sz(a)               (int)a.size()

const int N = 1e6 + 10;
int phi[N];

void solve()
{ 
    phi[1] = 1;
    for(int i = 2;i < N; ++i){
        phi[i] = i - 1;
    }

    for(int i = 2;i < N; ++i){
        for(int j = 2 * i;j < N; j += i){
            phi[j] -= phi[i];
        }
    }
    ll n, ans = 0;
    cin >> n;
    for(int i = 2;i <= n; ++i){
        ans += 2 * phi[i];
    }
    cout << ans + 1;
}   
 
int32_t main(){
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
}