#include<bits/stdc++.h>
using namespace std;
int he(int n){
	if(n==1) return 1;
	else return he(n-1)+n;	
}
int n,s=0;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
    	s=s+he(i);
	}
	cout<<s;

	return 0;
}

/**************************************************************
	Problem: 1148
	User: zhuanghaoxiang
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/