#include <bits/stdc++.h>
using namespace std;
int main(){
    int c,g=0,c1;
    cin>>c;
    for(int i=1;i<=c;i++){
        c1=i;
        for(int j=1;j<=c1;j++){
            g=g+j;
        }
    }
    cout<<g;
}
/**************************************************************
	Problem: 1148
	User: panyuchen
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/