IntMap.findMax m & \case
  (k,_) → flip IntMap.lookup m <$> [0..k]

numberOfSizes ∷ Int
numberOf
intMapList m              = IntMap.findMax m & \case
  (k,_) → flip IntMap.lookup m <$> [0..k]
intMapList m              = IntMap.findMax m & \case
  (k,_) → flip IntMap.lookup m <$> [0..k]