#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    firstnumber = 2*((k)*(k-1)//2) + 1
    sum = (k) * (2*firstnumber + (k-1) * 2) //2
    print(sum)
    

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