Kata

Description

An infinite number of shelves are arranged one above the other in a staggered fashion.
The cat can jump either one or three shelves at a time: from shelf i to shelf i+1 or i+3 (the cat cannot climb on the shelf directly above its head), according to the illustration:

                 ┌────────┐
                 │-6------│
                 └────────┘
┌────────┐       
│------5-│        
└────────┘  ┌─────► OK!
            │    ┌────────┐
            │    │-4------│
            │    └────────┘
┌────────┐  │
│------3-│  │     
BANG!────┘  ├─────► OK! 
  ▲  |\_/|  │    ┌────────┐
  │ ("^-^)  │    │-2------│
  │ )   (   │    └────────┘
┌─┴─┴───┴┬──┘
│------1-│
└────────┘

Input

Start and finish shelf numbers (always positive integers, finish no smaller than start)

Task

Find the minimum number of jumps to go from start to finish

Example

Start 1, finish 5, then answer is 2 (1 => 4 => 5 or 1 => 2 => 5)

Inspirers