///@author Sycamore, ZJNU
///@accepted_on 2017-01-24
#include<iostream>
using namespace std;
int main()
{
int N;
while (cin >> N)
cout << N*N*N *(N*N*N - 1) / 2 - 3 * (N - 1)*N*N << endl;
return 0;
}
原文：http://www.cnblogs.com/zjnu/p/7248074.html