#include<iostream>
#include<cstdio>
#include<vector>
#include<algorithm>
#include<functional>
using namespace std;
typedef long long int llint;
#define  pub push_back
int main(void){
	double n;
	llint ans;
	cin>>n;
	ans=(llint)(sqrt(n/3));
	if(ans==0){ ans++; }
	cout<<ans<<endl;
	return 0;
}