#include<bits/stdc++.h>
using namespace std;
int n;
int t=0,ts=0;
int s=1;
int main()
{
	cin>>n;
	while(n!=0)
	{
		n=n-s;
		s++;
		ts++;
	}
	for(int i=1;i<=ts;i++)
	{
		t=t+i*i;	
	}
	cout<<t;
	return 0;
}

/**************************************************************
	Problem: 2340
	User: hongyipin
	Language: C++
	Result: Time Limit Exceed
****************************************************************/