B'You are given a permutation p of integers from 0 to n-1 (each of them occurs exactly once). Initially, the permutation is not sorted (that is, p_i>p_{i+1} for at least one 1 <= i <= n - 1 ). The permutation is called X -sortable for some non-negative integer X if it is possible to sort the permutation by performing the operation below some finite number of times: Here & denotes the bitwise AND operation. Find the maximum value of X such that p is X -sortable. It can be shown that there always exists some value of X such that p is X -sortable. The input consists of multiple test cases. The first line contains a single integer t (1 <= t <= 10^4) -- the number of test cases. Description of test cases follows. The first line of each test case contains a single integer n (2 <= n <= 2 cdot 10^5) -- the length of the permutation. The second line of each test case contains n integers p_1, p_2, ..., p_n ( 0 <= p_i <= n-1 , all p_i are distinct) -- the elements of p . It is guaranteed that p is not sorted. It is guaranteed that the sum of n over all cases does not exceed 2 cdot 10^5 . For each test case output a single integer -- the maximum value of X such that p is X -sortable. In the first test case, the only X for which the permutation is X -sortable are X = 0 and X = 2 , maximum of which is 2 . Sorting using X = 0 : Sorting using X = 2 : In the second test case, we must swap p_1 and p_2 which is possible only with X = 0 . '...