B"You are given an array of integers a of length n . You can apply the following operation any number of times (maybe, zero): Find the minimum number of coins needed to make a non-decreasing. That is, a_1 <= a_2 <= ldots <= a_n . Each test contains multiple test cases. The first line of input contains a single integer t ( 1 <= t <= 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 <= 10^5 ) -- the length of the array a . The second line of each test case contains n integers a_1, a_2, ldots, a_n ( 1 <= a_i <= 10^9 ) -- the elements of the array a . It is guaranteed that the sum of n over all test cases does not exceed 10^5 . For each test case, output a single integer -- the minimum number of coins needed to make a non-decreasing. In the first test case, a is already sorted, so you don't have to spend any coins. In the second test case, the optimal sequence of operations is: "...