#include<iostream>
using namespace std;

int main(void){
  const double g = 9.8;
  const double height = 5.0;
  double v, y;
  int N;
  while(cin >> v){
    y = (v * v) / (2 * g);
    N = y / height + 1;
    if(y % height != 0)
      N++;
    
    cout << N << endl;
  }
  return 0;
}