#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    start= (k*(k-1))+1
    sum=0
    for i in list(range(k)):
        sum += start+(i*2)
    return sum
if __name__ == "__main__":
    k = int(input().strip())
    answer = sumOfGroup(k)
    print(answer)