Given an integer `k`, return the minimum number of Fibonacci numbers whose sum is equal to `k`. The same Fibonacci number can be used multiple times.

The Fibonacci numbers are defined as:

- `F1 = 1`
- `F2 = 1`
- `Fn = Fn-1 + Fn-2` for `n > 2.`

It is guaranteed that for the given constraints we can always find such Fibonacci numbers that sum up to `k`.

Example 1:

    Input: k = 7
    Output: 2
    Explanation: The Fibonacci numbers are: 1, 1, 2, 3, 5, 8, 13, ...
    For k = 7 we can use 2 + 5 = 7.

Example 2:

    Input: k = 10
    Output: 2
    Explanation: For k = 10 we can use 2 + 8 = 10.

Example 3:

    Input: k = 19
    Output: 3
    Explanation: For k = 19 we can use 1 + 5 + 13 = 19.

Constraints:

- `1 <= k <= 109`