#include<iostream>
#include<stdio.h>
#include<vector>
#define pb push_back
#define ll long long
using namespace std;
ll ans, n, m = 1;
int main()
{
	ios_base::sync_with_stdio(false);
	cin >> n;
	while(true)
	{
		ll cur = 3 * ((m * (m + 1)) / 2) - m;
		if(cur > n)
			break;
		if((n - cur) % 3 == 0)
			ans++;
		m++;
	}
	cout << ans;
	return 0;
}