Kata

Final kata of the series (highly recommended to compute layers and branch first to get a good idea), this is a blatant ripoff of the one offered on AoC.

Given a number, return the Manhattan distance considering the core of the spiral (the 1 cell) as 0 and counting each step up, right, down or left to reach a given cell.

For example, using our beloved 5x5 square:

17 16 15 14 13    4 3 2 3 4
18 05 04 03 12    3 2 1 2 3
19 06 01 02 11 => 2 1 0 1 2
20 07 08 09 10    3 2 1 2 3
21 22 23 24 25    4 3 2 3 4

And thus your code should behave like this:

distance(1) === 0
distance(5) === 2
distance(25) === 4
distance(30) === 5
distance(50) === 7

distance(1) == 0
distance(5) == 2
distance(25) == 4
distance(30) == 5
distance(50) == 7

distance(1) == 0
distance(5) == 2
distance(25) == 4
distance(30) == 5
distance(50) == 7

distance(1) == 0
distance(5) == 2
distance(25) == 4
distance(30) == 5
distance(50) == 7

distance(1) == 0
distance(5) == 2
distance(25) == 4
distance(30) == 5
distance(50) == 7

Distance(1) == 0
Distance(5) == 2
Distance(25) == 4
Distance(30) == 5
Distance(50) == 7

Just be ready for larger numbers, as usual always positive.

[Dedicated to swiftest learner I met in a long while]