#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <cstdio>
#include <functional>
#include <set>
#include <sstream>
#include <map>

using namespace std;

const double eps=1e-10;

int main()
{
	double v;
	while(cin>>v){
		unsigned long long l=1,r=1e16,h;

		while(l+1!=r){

//			cout<<l<<" "<<r<<endl;

			h=(l+r)/2;
			double vv=(5*h-5)/4.9*9.8*9.8;

			if(v*v>vv) l=h;
			else r=h;
		}

		if( abs(v*v-(5*l-5)/4.9*9.8*9.8)<eps ) cout<<l<<endl;
		else cout<<r<<endl;

	}

	return 0;
}