# -*- coding: utf-8 -*-
'''
Problem:
The sum of the squares of the first ten natural numbers is,
            1^2 + 2^2 + ... + 10^2 = 385
The square of the sum of the first ten natural numbers is,
            (1 + 2 + ... + 10)^2 = 552 = 3025
Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 − 385 = 2640.
Find the difference between the sum of the squares of the first N natural numbers and the square of the sum.
'''
from __future__ import print_function
n = int(raw_input())
suma = n*(n+1)/2
suma **= 2
sumb = n*(n+1)*(2*n+1)/6
print(suma-sumb)