B"Let's call a sequence of integers x_1, x_2, ... , x_k MEX-correct if for all i ( 1 <= i <= k ) |x_i - operatorname{MEX}(x_1, x_2, ... , x_i)| <= 1 holds. Where operatorname{MEX}(x_1, ... , x_k) is the minimum non-negative integer that doesn't belong to the set x_1, ... , x_k . For example, operatorname{MEX}(1, 0, 1, 3) = 2 and operatorname{MEX}(2, 1, 5) = 0 . You are given an array a consisting of n non-negative integers. Calculate the number of non-empty MEX-correct subsequences of a given array. The number of subsequences can be very large, so print it modulo 998244353 . Note: a subsequence of an array a is a sequence [a_{i_1}, a_{i_2}, ... , a_{i_m}] meeting the constraints 1 <= i_1 < i_2 < ... < i_m <= n . If two different ways to choose the sequence of indices [i_1, i_2, ... , i_m] yield the same subsequence, the resulting subsequence should be counted twice (i. xe2 x80 x89e. two subsequences are different if their sequences of indices [i_1, i_2, ... , i_m] are not the same). The first line contains a single integer t ( 1 <= t <= 10^5 ) -- the number of test cases. The first line of each test case contains a single integer n ( 1 <= n <= 5 cdot 10^5 ). The second line contains n integers a_1, a_2, ... , a_n ( 0 <= a_i <= n ). The sum of n over all test cases doesn't exceed 5 cdot 10^5 . For each test case, print a single integer -- the number of non-empty MEX-correct subsequences of a given array, taken modulo 998244353 . In the first example, the valid subsequences are [0] , [1] , [0,1] and [0,2] . In the second example, the valid subsequences are [0] and [1] . In the third example, any non-empty subsequence is valid. "...