#include<iostream>

using namespace std;



main(){
  double minv;
  while(cin >>minv){
    int i;
    double t = minv/9.8;
    double y;
    y = 4.9*t*t;
    double tall;
    for(i=1;y>=tall ; i++){
      tall = 5*i-5;
    }

    cout << --i << endl;


  }





  return 0;
}