Stalactites or Stalagmites?

Stalactites hang from the ceiling of a cave while stalagmites grow from the floor.

Create a function that determines whether the input represents "stalactites" or "stalagmites". If it represents both, return "both". Input will be a 2D list, with 1 representing a piece of rock, and 0 representing air space.

Examples

mineral_formation([
  [0, 1, 0, 1],
  [0, 1, 0, 1],
  [0, 0, 0, 1],
  [0, 0, 0, 0]
]) ➞ "stalactites"

mineral_formation([
  [0, 0, 0, 0],
  [0, 1, 0, 1],
  [0, 1, 1, 1],
  [0, 1, 1, 1]
]) ➞ "stalagmites"

mineral_formation([
  [1, 0, 1, 0],
  [1, 1, 0, 1],
  [0, 1, 1, 1],
  [0, 1, 1, 1]
]) ➞ "both"

Notes

• There won't be any examples where both stalactites and stalagmites meet (because those are called pillars).
• There won't be any example of neither stalactites or stalagmites.
• In other words, if the first list has 1s, return "stalactites". If the last list has 1s, return "stalagmites". If both have them, return "both".