#include<bits/stdc++.h>
using namespace std;
int main()
{
	int s=0;
	int a[5000];
	a[1]=1;
	int k=1;
	for(int i=2;i<5000;i++)
		{
			a[i]=a[i-1]+(i-1);
		}
	while (s<5000)
	{
		s+=a[k];
		k++;
	}
	cout<<s;
	return 0;
}
/**************************************************************
	Problem: 1146
	User: chenkexin
	Language: C++
	Result: Accepted
	Time:4 ms
	Memory:2072 kb
****************************************************************/