B"Alice and Bob play yet another game on an array a of size n . Alice starts with an empty array c . Both players take turns playing, with Alice starting first. On Alice's turn, she picks one element from a , appends that element to c , and then deletes it from a . On Bob's turn, he picks one element from a , and then deletes it from a . The game ends when the array a is empty. Game's score is defined to be the MEX ^ dagger of c . Alice wants to maximize the score while Bob wants to minimize it. Find game's final score if both players play optimally. ^ dagger The operatorname{MEX} (minimum excludant) of an array of integers is defined as the smallest non-negative integer which does not occur in the array. For example: Each test contains multiple test cases. The first line contains a single integer t ( 1 <= q t <= q 2 cdot 10^4 ) -- the number of test cases. The description of the test cases follows. The first line of each test case contains a single integer n ( 1 <= n <= 2 cdot 10^5 ). The second line of each test case contains n integers a_1, a_2, ldots, a_n ( 0 <= a_i < n ). It is guaranteed that the sum of n over all test cases does not exceed 2 cdot 10^5 . For each test case, find game's score if both players play optimally. In the first test case, a possible game with a score of 2 is as follows: At the end, c=[1,0] , which has a MEX of 2 . Note that this is an example game and does not necessarily represent the optimal strategy for both players. "...