#include <stdio.h>
#include <iostream>

using namespace std;

int main() {
	double a;
	double time;
	int kai;
	while (cin >> a) {
		time = a / 9.8;
		kai = (4.9 * time * time + 5) / 5 + 1;
		cout << kai << endl;
	}

	return 0;
}