#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,a[111]={0},b[111]={0},h=0;
    b[1]=1; 
    cin>>n;
    for(int i=1;i<=101;i++){
        a[i]=i;
    }
    for(int i=2;i<=101;i++){
         b[i]=a[i-1]+b[i-1];
    }
    for(int i=1;i<=n;i++){
        h=h+b[i]; 
    } 
    cout<<h;
    return 0;
}
/**************************************************************
	Problem: 1145
	User: wuweimo
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/