#include <iostream>
using namespace std;
int main(){
    int n;
    int sum = 0;
    cin>>n;
    while(n){
        int temp = 0;
        for(int i = 1;i<=n;i++){
            
            temp += i;
            sum += temp;
        }
        break;
    }
    cout<<sum;
    
    return 0;
}