#!/bin/python3

import sys

def sumFrom1ToN(n):
    return n*(n+1)//2

def sumOfGroup(k):
    start = (k-1)*k+1
    end = start+(2*k)
    #print("Start: {}, End: {}".format(start,end))
    s = 0
    for i in range(start,end,2):
        s += i    
    return s

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