#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    curr = int(k * (k + 1) / 2)
    pre = int(k * (k - 1) / 2)
    return getOddSum(curr) - getOddSum(pre) 
    
def getOddSum(n):
  return n ** 2 

if __name__ == "__main__":
    k = int(input().strip())
    answer = sumOfGroup(k)
    print(answer)