//0024 Physical Experiments

// élª¢Êu©çKXð©Rº³¹é
//v=9.8tAy=4.9t^2ÆÈé
//ªêéÌÉKvÈÅá¬xª^¦çêéÆ«A­È­ÆàrÌ½K©çÆ¹Îæ¢©
//½¾µArÌNKÌ³Í5N-5Æ·é

#include<iostream>
#include<cmath>
using namespace std;
double Square(double x){return x*x;}
int main(void)
{
	double y, v, t;
	while(cin >> v)
	{
		t = v/9.8;
		y = 4.9*Square(t);
		//y >= 5N-5
		//N <= y/5+1
		int N = static_cast<int>(ceil(y/5.0+1.0));
		cout << N << endl;
	}
	return 0;
}