#!/bin/python3

import sys
num = int(input())
val1 = (num*(num-1))//2
num1 = num+1
val2 = (num1*(num1-1))//2
a1 = 1
dis = 2
arr1 = ((val1)*((2*a1)+((val1-1)*dis)))//2
arr2 = ((val2)*((2*a1)+((val2-1)*dis)))//2
res = arr2 - arr1
print(res)