Solve the programming task below in a Python markdown code block.
Chef recently realized that he needs a haircut, and went to his favorite hair salon. At the salon, he found N customers waiting for their haircuts. From his past experience, Chef knows that the salon takes M minutes per customer. Only one person can get their haircut at a time.

For how many minutes will Chef have to wait before he can get his haircut?

------ Input Format ------ 

- The first line of input contains a single integer T, denoting the number of test cases. The description of T test cases follows.
- The first and only line of each test case contains two space-separated integers N and M, as described in the problem. 

------ Output Format ------ 

For each test case, print a single line containing one integer — the number of minutes that Chef will have to wait before he can get his haircut.

------ Constraints ------ 

$1 ≤ T ≤ 1000$
$0 ≤ N ≤ 1000$
$1 ≤ M ≤ 1000$

------ subtasks ------ 

Subtask #1 (100 points): Original constraints

----- Sample Input 1 ------ 
2
2 15
0 15

----- Sample Output 1 ------ 
30
0

----- explanation 1 ------ 
Test case $1$: There are $2$ customers waiting for the haircut and the salon will take $15$ minutes for each customer, hence Chef will have to wait for $30$ minutes before he can get his haircut.

Test case $2$: There are $0$ customers waiting for the haircut, therefore the Chef will not have wait to get the haircut.