#include<iostream>
using namespace std;

int main()
{
    int n;
    long long int ans[4001];
    long long int up = 6;

    ans[1] = 4;
    for(int i=2; i<4001; i++){
        ans[i] += up + ans[i-1];
        up += i+2;
    }

    while(cin >> n)
    {
        cout << ans[n] << endl;
    }

    return 0;
}