#include <iostream>
#include <cmath>

using namespace std;

int main()
{
  double speed, v, t;
  int height;
  int N;

  while (cin >> speed) {
    N = 1;
    while (1) {
      height = 5 * N - 5;
      t = sqrt(height / 4.9);

      v = 9.8 * t;
      if (v >= speed) {
        break;
      }

      N++;
    }

    cout << N << endl;
  }

  return 0;
}