Kata

your task is to implement a method/function that takes a posistive integer and returns its single digit sum of digits **i.e. keep summing the digits till only one digit remains.

Examples: //for Java
sumDigits(4523) = 4 + 5 + 2 +3 = 14 = 1 + 4 = 5
here sumDgits(4523) should return 5
sumDigits(65536) = 6 + 5 + 5 + 3 + 6 = 25 = 2 + 5 = 7
here sumDgits(65536) should return 7

Examples: //for Ruby and Python
sum_digits(4523) = 4 + 5 + 2 +3 = 14 = 1 + 4 = 5
here sum_digits(4523) should return 5
sum_digits(65536) = 6 + 5 + 5 + 3 + 6 = 25 = 2 + 5 = 7
here sum_digits(65536) should return 7