#!/bin/python3

import sys

def sumOfGroup(k):
    sumN1 = 0
    i = 0
    t = k + (k-1)**2
    while i < k :
        sumN1 += t + 2*i
        i += 1
    return sumN1    

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