/*
 * Problem: AOJ0024
 * Author: YOUSIKI
 * Date: 2016/6/23
 */
#include<bits/stdc++.h>
using namespace std;
signed main(void){
	ios::sync_with_stdio(false);
	double input;
	while(cin>>input){
		/*
		 * v=9.8*t
		 * y=4.9*t^2
		 * so y=4.9*(v/9.8)^2
		 *     =v^2/(9.8*2)
		 * but y must can be written into a form like
		 *     5*(n-1)
		 * so we have to find the min(n-1) to make y>=5*(n-1)
		 * and it's surely ceil(y/5)
		 */
		cout<<ceil(pow(input,2)/(9.8*2.0)/5.0+1.0)<<endl;
	}
}