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

}
/**************************************************************
	Problem: 1146
	User: houshanglin
	Language: C++
	Result: Accepted
	Time:3 ms
	Memory:2072 kb
****************************************************************/