#!/bin/python3

import sys

def sumOfGroup(k):
    group = [(k * (k+1)) - 1]
    i = 0
    while len(group) < k:
        group.append(group[i] - 2)
        i += 1
    return sum(group)

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