#!/bin/python3

import sys

def grp_last_idx(k):
    return (k + 1) * k // 2

def grp_sum_to_last(k):
    n = grp_last_idx(k)
    return n * n

def sumOfGroup(k):
    return grp_sum_to_last(k) - grp_sum_to_last(k - 1)

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