#include <iostream>
using namespace std;

int main() {
	
	int n = 0;
	int ret = 0;		//表达式的值，不断变化
	int sum = 0;		//最终结果
	cin >> n;

	//循环遍历
	for (int i = 1; i <= n; i++) {
		ret += i;
		sum += ret;
	}

	cout << sum;

	system("pause");
	return 0;
 }