#include <iostream>
using namespace std;
int t(int n){
	int f;
	if(n==1)f=1;
	else if(n==2)f=2;
	else f=t(n-1)+n-1;
	return f;
}
int main()
{
	int s=0,i=1;
	while(s<5000){
		s=s+t(i);
		i++;
	}
	cout<<s;
	return 0;
}
/**************************************************************
	Problem: 1146
	User: xuanhua
	Language: C++
	Result: Accepted
	Time:4 ms
	Memory:2072 kb
****************************************************************/