#include<bits/stdc++.h>
using namespace std;
int n,c=0;
int a(int s){
	if(s==1) return 1;
	else return a(s-1)+s;
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		c=c+a(i);
	}
	cout<<c;
}
/**************************************************************
	Problem: 1148
	User: zhuanghaoxiang
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/