Number of \textbf{P} is said to be inverted in the number \textbf{N}, if the inverted decimal entry coincides with one decimal another. For example, inverted for \textbf{3489} will be \textbf{9843}, but to \textbf{2009100} will be \textbf{0019002} or, excluding leading zeros, just \textbf{19002}. Given a positive integer \textbf{N}. Find the largest number of \textbf{M} such that it will, when added with its inverted, will give a fixed number \textbf{N}. \InputFile The first line contains one integer \textbf{N} (1 <= \textbf{N} <= \textbf{10^100^\{ \}^000}). \OutputFile Bring one number - the answer to the question of the problem. If the desired number does not exist, output a \textbf{0}.