Given an integer array nums, return the largest integer that only occurs once. If no integer occurs once, return -1.

 

Example 1:

Input: nums = [5,7,3,9,4,9,8,3,1]
Output: 8
Explanation: The maximum integer in the array is 9 but it is repeated. The number 8 occurs only once, so it is the answer.

Example 2:

Input: nums = [9,9,8,8]
Output: -1
Explanation: There is no number that occurs only once.

 

Constraints:

• 1 <= nums.length <= 2000
• 0 <= nums[i] <= 1000