#include <cmath>
#include <cstdio>
#include <iostream>

using namespace std;

const double eps = 1e-12;

int main() {
	double v;
	while (scanf("%lf", &v) != EOF) {
		double n = (v * v / 19.6 + 5) / 5.0;
		if (!(fabs(n - (int)n) < eps)) n += 1;
		printf ("%d\n", (int)n);
	}
	return 0;
}