\includegraphics{https://static.e-olymp.com/content/0f/0f01b60f21ce234a4c69f3da04f746c33b2ed5c0.jpg} The garland consists of \textbf{N} bulbs for general wire. One end is fixed at a given height \textbf{A} mm (\textbf{H_1} = \textbf{A}). Due to the gravity bends garland: the height of each non lamp at \textbf{1} mm less than the average height of the nearest-neighbor (\textbf{H_i} = (\textbf{H_i}_\{ - 1\} + \textbf{H_i}_\{ + 1\})/\textbf{2} - \textbf{1} for \textbf{1} < \textbf{i} < \textbf{N}). Required to find the minimum height of the second end \textbf{B} (\textbf{B} = \textbf{H_N}) provided that none of the bulbs should not lie on the ground (\textbf{H_i} > \textbf{0} for \textbf{1} ≤ \textbf{i} ≤ \textbf{N}). \InputFile The first line contains two numbers, \textbf{N} and \textbf{A}. \textbf{3} ≤ \textbf{N} ≤ \textbf{1000} - integer, \textbf{10} ≤ \textbf{A} ≤ \textbf{1000} - real. \OutputFile Print a single real number \textbf{B} with the two characters after the decimal point.