import java.util.Locale;

public class Euler317 {
    public static String solve() {
        double h = 100.0;
        double v = 20.0;
        double g = 9.81;

        double a = h + (v * v) / (2.0 * g);
        double b = g / (2.0 * v * v);

        double ans = Math.PI * a * a / (2.0 * b);
        return String.format(Locale.US, "%.4f", ans);
    }

    public static void main(String[] args) {
        System.out.println(solve());
    }
}