#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    #nums = [ i for i in range(1,1000000) if i%2 != 0]
    #slc = nums[k: 2*k]
    num = k*(k-1)+1
    tot = 0
    for i in range(num, num + 2*k, 2 ):
        tot = tot + i
    return tot

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