#!/bin/python

import sys

def sumOfGroup(k):
    if k==1: return 1
    if k==2: return 8
    return (k)+(k+1)*(k-1)*k
    # Return the sum of the elements of the k'th group.

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