#include<bits/stdc++.h>
using namespace std;  
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) for(int i=0;i<(n);i++)  
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
#define pii pair<int,int>
#define piii pair<int,pii>
#define mp make_pair
#define pb push_back  
#define ALL(a) (a).begin(),(a).end()
#define FST first
#define SEC second  
const int INF = (INT_MAX/2);
const double eps = 1e-14;
const double PI = M_PI;  
#define DEB cout<<"!"<<endl
#define SHOW(a,b) cout<<(a)<<" "<<(b)<<endl  
#define DIV 1000000007

int main(){
	multimap<int,int> t1,t2; // w,v
	ll input;
	cin >> input;
	
	cout << ceil(sqrt(input)/3.0) << endl;
	
	return 0;
}