Sum of digits

Problem

A checksum adds up the digits of an account number. Write digit_sum(n) that returns the sum of the digits of n and print it.

Example

Input

Output

4 + 8 + 2 + 1.

Try the problem first. Open one hint at a time.

Hint 1

n % 10 is the last digit and n // 10 removes it.

Hint 2

Loop while n is greater than 0 and add each last digit to a total.

Write your Python code, run it on the examples and submit it to hidden tests.