#include<bits/stdc++.h>
using namespace std;
int k,n,i=1;
unsigned long long *a;
int main()
{
	cin>>k;
	n=k;
	a=new unsigned long long [k+5];
	while(n)
	{
		for(int j=1;j<=i;j++)
		{
			a[k-n+1]=a[k-n]+i;
			n--;
		}
		i++;
	}
	cout<<a[k];
	return 0;
}