#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long 
#define ld long double
#define pii pair<int, int>
#define pb push_back
#define eb emplace_back
#define int ll 

using namespace std;

signed main()
{
    #ifndef TEST 
        freopen("fractii.in", "r", stdin);
        freopen("fractii.out", "w", stdout);
    #endif
    ios_base :: sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);
    
    int n;
    cin >> n;
    vector<int> phi(n + 1);
    for (int i = 1; i <= n; i++)
    {
        phi[i] = i;
    }
    for (int i = 2; i <= n; i++)
    {
        if (phi[i] == i)
        {
            for (int j = i; j <= n; j += i)
            {
                phi[j] = phi[j] / i * (i - 1);
            }
        }
    }
    int ans = 0;
    for (int i = 1; i <= n; i++)
    {
        ans += phi[i];
    }
    cout << ans * 2 - 1;
    return 0;
}