#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 h=0;
	for(int i=1;h<=5000;i++){
		h=h+f(i);
	}
	cout<<h;
	return 0;
}
/**************************************************************
	Problem: 1146
	User: hongjiaming
	Language: C++
	Result: Accepted
	Time:4 ms
	Memory:2072 kb
****************************************************************/