#!/bin/python3

import sys

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

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