#include<bits/stdc++.h>
using namespace std;
int f(int n){
    int r=0;
    if(n==1) return 1; 
    else r=f(n-1)+n;
    return r;
}
int main(){
    int n,h=0;
    cin>>n;
    for(int i=1;i<=n;i++){
        h=h+f(i);
    }
    cout<<h;
    return 0;
}
/**************************************************************
	Problem: 1148
	User: hongjiaming
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/