indices = [
  [-7, 1, 5, 2,-4, 3, 0],
  [2, 4, 6],
  [2, 9, 2],
  [1,-1, 1,-1, 1,-1, 1]
]
Enum.each(indices, fn list ->
  IO.puts "#{inspect list} => #{inspect Equilibrium.index(list)}"
end)