#!/bin/python3

import sys
mylist = []
counter = 1
total = 0
def sumOfGroup(k):
    global counter
    global total
    for f in range(1,k+1):
        mylist.append([])
        for k in range(1,f+1):
            mylist[-1].append(counter)
            counter +=2
    for f in mylist[k-1]:
        total = total + f
    return total

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