#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;
int main() {
	double d;
	double EPS = 1e-5;
	while(scanf("%lf", &d) == EOF) {
		cout << ceil((4.9 * pow(d / 9.8, 2.0) + 5.0 + EPS) / 5.0) << endl;
	}
	return 0;
}