#!/bin/python

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    m=k*(k+1)
    sum=0
    for i in range(0,k):
        sum =sum+(m-(2*i+1))
    return sum

if __name__ == "__main__":
    k = int(raw_input().strip())
    answer = sumOfGroup(k)
    print answer