#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: linyuhang
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/