#include<iostream>
#include<cmath>
using namespace std;

double speed(double x) {
	double time = x / 9.8;
	double y = 4.9*time*time;
	double f = (y / 5)+1 ;
	f = floor(f);
	int g = static_cast<int>(f);
	return g;
}

int main() {
	double x;
	while (cin >> x) {
		cout << speed(x) << endl;
	}
	return 0;
}