#include<bits/stdc++.h>
using namespace std;
int n,h=0;
int a(int s){
    if(s==1) return 1;
    else return a(s-1)+s;
}
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        h=h+a(i);
    }
    cout<<h;
}
/**************************************************************
	Problem: 1148
	User: hang
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/