#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    i=(k*(k-1))+1
    add=0
    while(k>0):
        add+=i
        i+=2
        k-=1
    return add

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