#include<bits/stdc++.h>
using namespace std;
int main(){
	int i,n,w=1,s=0;
	cin>>n;
	for(i=1;s<=n;i++){
		for(w=1;w<=i;w++){
			s+=i;
		}
	}
	cout<<s;
	return 0;
}
/**************************************************************
	Problem: 1520
	User: houshanglin
	Language: C++
	Result: Wrong Answer
****************************************************************/