#include<iostream>
using namespace std;
int main(){
  double v,y,t;
  int h,a,b;
  while(cin>>v){
  t = v / 9.8;
  y = 4.9 * t * t;
  h = (y+5)/5;
  a = y+5;
  b = a % 5; 
    if(b!=0) h = h + 1;
  cout << h << endl;
  }
  return 0;
}