#include <iostream>
#include <cmath>
using namespace std;
int num(int n){
	int r;
	if(n==1){
		r=1;
	}else{
		r=num(n-1)+n-1;
	}	
	
	return r;
}
int main(){
	int n,i,s;
	s=0;
	cin>>n;
	for(i=1;i<=n;i++){
		s=s+num(i);
	}
	cout<<s<<endl;
}
/**************************************************************
	Problem: 1145
	User: admin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/