#!/bin/python3

import sys

def nth_odd(n):
    return 2 * n + 1

def sum_k(k):
    total = 0
    for i in range(k, -1, -1):
        total += i
    return total

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    total = 0
    k_sum = sum_k(k - 1)
    for i in range(k_sum, k_sum + k):
        total += nth_odd(i)
    return total
    

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