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

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