import java.util.Locale;

public class Euler697 {
    public static String solve() {
        double n = 10000000.0;
        double z = 0.6744897501960817;

        double term = 1.0 - 1.0 / (9.0 * n) + z / Math.sqrt(9.0 * n);
        double c = n * Math.pow(term, 3);

        double ans = c / Math.log(10.0);

        return String.format(Locale.US, "%.2f", ans);
    }

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