hdu1290

=(n^3+5n)/6+1

/** \brief hdu 1290
 *
 * \param date 2014/7/25
 * \param state AC
 * \return
 *
 */

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    //cout << "Hello world!" << endl;
    //freopen("input.txt","r",stdin);
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        cout<<(n*n*n+5*n)/6+1<<endl;
    }
    return 0;
}