/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2020.06.13 02:47:50
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;

int main() {
    int n;cin >> n;
    if (n == 1) {
        cout << 0 << endl;
        return 0;
    }
    ll ans = 0;
    ll l = 1, r = n;
    ans += l * r;
    l++;
    r--;
    while(l < r) {
        ans += l * (r+1) + (l-1) * r;
        l++;r--;
    }
    if (l == r) ans += 2 * l * l;
    else ans += l * r;
    cout << ans << endl;
    return 0;
}