B"To celebrate his recovery, k1o0n has baked an enormous n metres long potato casserole. Turns out, Noobish_Monk just can't stand potatoes, so he decided to ruin k1o0n's meal. He has cut it into k pieces, of lengths a_1, a_2, ... , a_k meters. k1o0n wasn't keen on that. Luckily, everything can be fixed. In order to do that, k1o0n can do one of the following operations: Help k1o0n to find the minimum number of operations he needs to do in order to merge the casserole into one piece with length n . For example, if n=5 , k=2 and a = [3, 2] , it is optimal to do the following: Each test contains multiple test cases. The first line contains the number of test cases t ( 1 <= t <= 10^4 ). Description of each test case consists of two lines. The first line contains two integers n and k ( 2 <= n <= 10^9 , 2 <= k <= 10^5 ) -- length of casserole and the number of pieces. The second line contains k integers a_1, a_2, ldots, a_k ( 1 <= a_i <= n - 1 , sum a_i = n ) -- lengths of pieces of casserole, which Noobish_Monk has cut. It is guaranteed that the sum of k over all t test cases doesn't exceed 2 cdot 10^5 . For each test case, output the minimum number of operations K1o0n needs to restore his pie after the terror of Noobish_Monk. "...