#!/bin/python3

import sys

def firstnumber(k):
    if k == 1:
        return 1
    else:
        return(k * (k-1) +1) 

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    resultado = 0
    for i in range(0,k):
        resultado += firstnumber(k) + 2*i
    return resultado
if __name__ == "__main__":
    k = int(input().strip())
    answer = sumOfGroup(k)
    print(answer)