#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a[111]={0},b[111]={0},h=0;
	b[1]=1; 
	cin>>n;
	for(int i=1;i<=101;i++){
		a[i]=i;
	}
	for(int i=2;i<=101;i++){
		 b[i]=a[i-1]+b[i-1];
	}
	for(int i=1;i<=n;i++){
		h=h+b[i]; 
	} 
	cout<<h;
	return 0;
}
/**************************************************************
	Problem: 1145
	User: panyuchen
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/