#!/bin/python3

import sys

def sumOfGroup(k):
    l=0
    sum=(k*(k-1))+1
    sum1=0
    while l<k:
        sum1=sum1+sum
        sum=sum+2
        l=l+1
    return sum1

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