#include<bits/stdc++.h>
using namespace std;
int f(int n){
    if(n==1) return 1;
    else return f(n-1)+n;
}
int main(){
    int n,s=0;
    cin>>n;
    for(int i=1;i<=n;i++){
        s=s+f(i);
         
    }
    cout<<s;
 
 
    return 0;
}
 
/**************************************************************
	Problem: 1148
	User: wangchenyu
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2072 kb
****************************************************************/