#!/bin/python3

a = int(input())
x = 1
y = 0
num = 2
for i in range(0,a-1):
	x = x + num
	num = num + 2

y = []
for i in range(0,a):
	y.append(x)
	x = x + 2
summ = 0
for i in range(0,len(y)):
	summ = summ + y[i]
print(summ)