[
  [[1, "a"], [2, "a"], [3, "a"]],
  [[1, "a"], [2, "a"], [3, "b"]],
  [[1, "a"], [2, "b"], [3, "a"]],
  [[1, "a"], [2, "b"], [3, "b"]],
  [[1, "b"], [2, "a"], [3, "a"]],
  [[1, "b"], [2, "a"], [3, "b"]],
  [[1, "b"], [2, "b"], [3, "a"]],
  [[1, "b"], [2, "b"], [3, "b"]],
]