B. Candies Divisiontime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputSanta has n candies and he wants to gift them to k kids. He wants to divide as many candies as possible between all k kids. Santa can't divide one candy into parts but he is allowed to not use some candies at all.Suppose the kid who recieves the minimum number of candies has a candies and the kid who recieves the maximum number of candies has b candies. Then Santa will be satisfied, if the both conditions are met at the same time:  b - a \le 1 (it means b = a or b = a + 1);  the number of kids who has a+1 candies (note that a+1 not necessarily equals b) does not exceed \lfloor\frac{k}{2}\rfloor (less than or equal to \lfloor\frac{k}{2}\rfloor). \lfloor\frac{k}{2}\rfloor is k divided by 2 and rounded down to the nearest integer. For example, if k=5 then \lfloor\frac{k}{2}\rfloor=\lfloor\frac{5}{2}\rfloor=2.Your task is to find the maximum number of candies Santa can give to kids so that he will be satisfied.You have to answer t independent test cases.InputThe first line of the input contains one integer t (1 \le t \le 5 \cdot 10^4) — the number of test cases.The next t lines describe test cases. The i-th test case contains two integers n and k (1 \le n, k \le 10^9) — the number of candies and the number of kids.OutputFor each test case print the answer on it — the maximum number of candies Santa can give to kids so that he will be satisfied.ExampleInput
5
5 2
19 4
12 7
6 2
100000 50010
Output
5
18
10
6
75015
NoteIn the first test case, Santa can give 3 and 2 candies to kids. There a=2, b=3,a+1=3.In the second test case, Santa can give 5, 5, 4 and 4 candies. There a=4,b=5,a+1=5. The answer cannot be greater because then the number of kids with 5 candies will be 3.In the third test case, Santa can distribute candies in the following way: [1, 2, 2, 1, 1, 2, 1]. There a=1,b=2,a+1=2. He cannot distribute two remaining candies in a way to be satisfied.In the fourth test case, Santa can distribute candies in the following way: [3, 3]. There a=3, b=3, a+1=4. Santa distributed all 6 candies.
5
5 2
19 4
12 7
6 2
100000 50010

5 18 10 6 75015 
['math', '*900']