# Repeated Addition

Given a positive integer `n`

, sum all of its digits to get a new number. Repeat this operation until the new number is less than `10`

and return it.

**Constraints**

`1 ≤ n < 2 ** 31`

https://binarysearch.com/problems/Repeated-Addition

## Examples

### Example 1

**Input**

- n =
`8835`

**Output**

- answer =
`6`

**Explanation**

- 8 + 8 + 3 + 5 = 24
- 2 + 4 = 6

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