#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;

int main() {
  ll N; cin >> N;
  if(N==1){
    cout << 1 << endl;
    return 0;
  }
  N /= 3;
  ll ans = (int)sqrt(N);
  cout << ans << endl;
}