#!/bin/python

import sys

def sumOfGroup(k):
    first_num = k*(k-1) + 1
    mid_num = first_num + (k-1)
    return mid_num * 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