#include <iostream>

using namespace std;

int main()
{
  double v;
  while (cin >> v)
  {
    double t = v / 9.8;
    double y = 4.9 * t * t;

    for (int N = 1;; ++N)
      if ((5 * N - 5) > y) {
	cout << N << endl;
	break;
      }
  }
  
  return 0;
}