#!/bin/python

import sys

def sumOfGroup(k):
    diff = 2
    odd =1
    for i in range(k-1):
        odd=odd+diff
        diff +=2
    add=0
    for i in range(k):
        add=add+odd
        odd+=2
    return add

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