# Recursive Sum of Digits

You are asked to create a recursive function to calculate the sum of all the digits of a given positive integer

`n`

.The only line of the input contains a positive integer

`n`

.The function should return a single integer - the sum of the digits of the input number

`n`

.Input | Output |

1234 | 10 |

4567 | 22 |

999 | 27 |

Note: The function should use recursion, meaning the function should call itself to solve the problem. It should not use any loops like for or while.

#### Constraints

Time limit: 2 seconds

Memory limit: 512 MB

Output limit: 1 MB