Given an integer array nums, find the first element in nums whose frequency of occurrence is unique among all distinct elements in the array.

An element has a unique frequency if no other distinct value appears in nums the exact same number of times.

Return the value of this first element. If no element possesses a unique frequency, return $-1$.

Constraints:

• $1 \leq$ nums.length $\leq 10^5$

• $1 \leq$ nums[i] $\leq 10^5$

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