#include <iostream>

using namespace std;

int main()
{
  double v;
  while (cin >> v)
  {
    double t = v / 9.8;
    double y = 4.9 * t * t;
    
    int N = (y + 5) / 5 + 1;
	cout << N << endl;
  }
  
  return 0;
}