#include <bits/stdc++.h>
#include <iostream>
#include <cstdio>
#include <string>
#include <string.h>

using namespace std;

int main() {
  int n;
  cin >> n;
  
  cout << n/3 << endl;
}
#include<bits/stdc++.h>
using namespace std;

// Returns floor of square root of x
int floorSqrt(int x)
{
    // Base cases
    if (x == 0 || x == 1)
    return x;

    // Staring from 1, try all numbers until
    // i*i is greater than or equal to x.
    int i = 1, result = 1;
    while (result <= x)
    {
      i++;
      result = i * i;
    }
    return (i - 1)*(i-1);
}

// Driver program
int main()
{
    int x ;
    cin>>x;
    cout << floorSqrt(x) << endl;
    return 0;
}
