#include<bits/stdc++.h>
using namespace std;
int f(int n){
	int r;
	if(n==1) r=1;
	else r=f(n-1)+n-1;
	return r;	
		
}

int main(){
	int n,s=0;
	cin>>n;
	for(int i=1;i<=n;i++){
		s=s+f(i);
	}
	cout<<s;

	return 0;
}

/**************************************************************
	Problem: 1145
	User: wuzihang
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/