#!/bin/python3

import sys

first_val = [0,1]
for k in range(2,10**6+1):
    first_val.append(first_val[k-1]+(k-1)*2)

    

def sumOfGroup(k):
    #2*sum[0,k) + first_val[k]*k
    return 2*k*(k-1)//2 + first_val[k]*k
    
k = int(input().strip())
answer = sumOfGroup(k)
print(answer)