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