#!/bin/python3

import sys

def sumOfGroup(k):
    last = k - 1
    total = 0
    for i in range(last, 0, -1):
        total += i
    startOdd = total * 2 + 1
    oddTotal = 0
    while k > 0:
        oddTotal += startOdd
        startOdd +=2
        k -=1
    return oddTotal

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