Given an integer array nums and an integer k, consider every contiguous subarray of nums whose length is exactly k. A subarray is valid if all of its elements are distinct. Return the maximum possible sum among all valid subarrays. If no valid subarray exists, return $0$.

Constraints:

• $1 \leq$ k $\leq$ nums.length $\leq 10^5$

• $1 \leq$ nums[i] $\leq 10^5$

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