1def assert_equal(x, y)
 2  raise [x, y].inspect unless x == y
 3end
 4
 5class Solution
 6  def self.run(n)
 7    f(n + 1)
 8  end
 9
10  def self.f(n)
11    n <= 1 ? n : f(n - 1) + f(n - 2)
12  end
13end
14
15=begin
16  --
17    |
18     --
19       |
20        --
21          |
22           --
23             |
24
251: 1, 1, 1, 1
262: 1, 1, 2
273: 1, 2, 1
284: 2, 1, 1
295: 2, 2
30=end
31
32assert_equal(5, Solution.run(4))
33assert_equal(8, Solution.run(5))
34puts "Yay!"