class Solution:
    def removeDuplicates(self, nums: list[int]) -> int:
        if len(nums) <= 1:
            return len(nums)

        l = 1
        for r in range(1, len(nums)):
            if nums[r] != nums[r - 1]:
                nums[l] = nums[r]
                l += 1

        return l

items = [2, 10, 10, 10, 20, 30, 30, 40, 40, 40, 50]
result = Solution().removeDuplicates(items)
print(result, items)