#include<iostream>
#include<cmath>
using namespace std;
int main(){
  double height;

  while(cin >> height){
      double N,t;
    for(int i=1;;i++){
      N = 5*i - 5;
      t = sqrt(N/4.9);
      if(height <= 9.8*t){
	cout << i << endl;
	break;
      }
    }
  }
}