Please solve the programming task below using a self-contained code snippet in a markdown code block.

You are given an integer array nums. Each element in nums is 1, 2 or 3. In each operation, you can remove an element from nums. Return the minimum number of operations to make nums non-decreasing.
 
Please complete the following python code precisely:
```python
class Solution:
    def minimumOperations(self, nums: List[int]) -> int:
```