Problems

# License Software

# License Software

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.

**Input **

One number **n** (**0** ≤ **n **≤ **2 ^{31}**

^{}-

**1**).

**Output**

Print one number - the answer to the challenge.

Input example #1

123

Output example #1

6