#include <iostream>
using namespace std;

#define EPS (1e-6)

int main(){
	double v, y, t, n;
	int i;
	while(cin >> v){
		t = v/9.8;
		y = 4.9*t*t;
		n = y/5.0 + 1.0;
		i = 0;
		while(n - (double)i > EPS){
			i++;
		}
		cout << i << endl;
	}
	return 0;
}