// -*- coding: utf-8 -*-
// Last-Updated : <2014/06/19 00:45:07 by samui>

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <string>
#include <vector>
#include <climits>
#define MP(a, b) make_pair(a, b)
#define X first
#define Y second
#define rep(i,n) for(int (i) = 0; (i) < (int)(n); ++(i))
#define rer(i,l,n) for(int (i) = l; (i) <= (int)(n); ++(i))
#define reu(i,l,n) for(int (i) = l; (i) < (int)(n); ++(i))
template<typename T,typename U> inline void amin(T &x,U y){ if(y<x) x = y;}
template<typename T,typename U> inline void amax(T &x,U y){ if(x<y) x = y;}
template<typename TYPE,std::size_t SIZE>
std::size_t len(const TYPE (&array)[SIZE]){return SIZE;}
void abc(float x);
int main(int argc, char *argv[])
{
  float a;
  while(std::cin>>a){
    abc(a);
  }
  return 0;
}
void abc(float x)
{

  float t = x/9.8;
  float y = t*t*4.9;;
  float ans = int((y+5)/5.0);;
  while(ans*5-5<y)
    ++ans;
    std::cout<<ans<<std::endl;
}