#!/bin/python3

import sys

def sumOfGroup(k):
    # first get the the first element of the kth set
    # ie k = 4, k1 is the ((1 + 2 + 3) + 1)th element of the odd number sequence
    # use a for loop
    k1 = 1
    for i in range(0,k):
        k1 += i
    # all odd numbers are written as 2k-1
    # so we can form the sum of the set using this notation
    sum_k = 0
    for i in range(0,k):
        sum_k += 2*(k1+i) - 1
    
    return sum_k

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