#include<bits/stdc++.h>
using namespace std;
int f(int n)
{
	int r=0;
	if(n==1)
	{
		r=1;
	}
	else
	{
		r=f(n-1)+n-1;
	}
	return r;
}
int main()
{
	int s=0;
	int i=1;
	while(s<5000)
	{
		s=s+f(i);
		i=i+1;
	}
	cout<<s;
	return 0;
}

/**************************************************************
	Problem: 1146
	User: chenkexin
	Language: C++
	Result: Accepted
	Time:4 ms
	Memory:2072 kb
****************************************************************/