The numbers from \textbf{1} to \textbf{n} are written on a paper in increasing order. Between each pair of adjacent digits (and before the first) alternately \textbf{+} and \textbf{- are placed}. Find the resalt of this expression. For example, if \textbf{n} = \textbf{12}, then it is easy to see that the sum equals to five: \textbf{+ 1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + 9 - 1 + 0 - 1 + 1 - 1 + 2 = 5} \InputFile The first line contains an integer \textbf{n} (\textbf{1 }≤ \textbf{n }≤ \textbf{10^15}). \OutputFile Print the result of the given expression