#include <bits/stdc++.h>

using namespace std;

int n;
vector <int> eulerInd;

void euler()
{
    eulerInd.resize(n + 1);
    for(int i = 1; i <= n; i ++)
        eulerInd[i] = i;

    for(int i = 2; i <= n; i ++)
    {
        if(eulerInd[i] == i)
            for(int j = i; j <= n; j += i)
                eulerInd[j] = 1ll * eulerInd[j] * (i - 1) / i;
    }

//    for(int i = 1; i <= n; i ++)
//        cout << i << " " << eulerInd[i] << "\n";
//    cout << "\n";
}

int main()
{
    ios_base :: sync_with_stdio(0);
    cin.tie(0);

    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);

    cin >> n;

    euler();

    long long ans = 0;
    for(int i = 1; i <= n; i ++)
        ans += eulerInd[i];

    cout << 2 * ans - 1;
    return 0;
}