#!/bin/python3

import sys

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

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