Task
📝 **Task:** Write `lis_length(nums)` returning the LIS length. Print `lis_length([10, 9, 2, 5, 3, 7, 101, 18])`. Expected: 4 (2,3,7,101 or 2,5,7,101 etc.)
📋 Implement the function above. Tests run automatically.
💡 **Hint:** Re-read the theory if stuck.