#include <iostream>
#include <cmath>

using namespace std;

int main() {
  double v;
  while (cin >> v) {
    double t = v / 9.8;
    double h = 4.9 * t * t;
    double n = (h+5)/5;
    int ans = ceil(n);
    cout << ans << endl;

  }
  return 0;
}