#!/usr/local/bin/ruby
class P
  def a
    print("P-a")
    b
  end

  def b
    print(P-b")
  end
end

class C < P
  def a
    print("C-a")
    b
  end

  def b
    print(C-b")
  end
end
p= P.new
p.a
p.b