#!/bin/python3

import sys

#group = [i for i in range(1, 1000001, 2)]

def sumOfGroup(k):
    startVal = k * (k-1) + 1
#    print(startVal)
    kList = [startVal]
    for i in range(k-1):
        startVal += 2
        kList.append(startVal)
    return sum(kList)

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