#include<bits/stdc++.h>
using namespace std;
int f(int n){
	int r=0;
    if(n==1) r=1;
    else r=f(n-1)+n;
	return r; 
}
int main(){
	int n,s=0; 
    cin>>n;
	for(int i=1;i<=n;i++){
	 s=s+f(i)
}
cout<<s;
}
/**************************************************************
	Problem: 1148
	User: wengsihan
	Language: C++
	Result: Compile Error
****************************************************************/