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:
- If the amount is less than ten-digit number, then the digital root is the sum of digits of that number.
- Otherwise, the digital root of a number equal to the digital root of the sum of its digits.
One number n (0 ≤ n ≤ 231- 1).
Print one number - the answer to the challenge.