#include<iostream>
using namespace std;


int digui(int n);

int main(){
	
	int s=0,k=1;
	

	while(s<=5000){
		s=s+digui(k);
		k++;
	}
	cout<<s<<endl;
	
}

int digui(int n){

	if(n==1){
		return 1;
	} else{
	
		return (n-1)+digui(n-1);
	}
}

/**************************************************************
	Problem: 1146
	User: admin
	Language: C++
	Result: Accepted
	Time:4 ms
	Memory:2072 kb
****************************************************************/