As you know, to verify the licensed software used by the serial number and reshistratsionnye keys. You, as a leading developer of verification of license software was developed the idea of reliable in-a-kind system. It Is based on the digital roots of numbers. Now you need to write a program that defines the digital root of this number. For an arbitrary number of digital root is defined as follows: \begin{enumerate} \item If the amount is less than ten-digit number, then the digital root is the sum of digits of that number. \item Otherwise, the digital root of a number equal to the digital root of the sum of its digits. \end{enumerate} \textbf{Input } One number \textbf{n} (\textbf{0} ≤ \textbf{n }≤ \textbf{2^31}^\{ \}- \textbf{1}). \textbf{Output} Print one number - the answer to the challenge.