Chef and the Hair Salon solution|February long 2022 (div 3)(rated)

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

• $1 \leq T \leq 1000$
• $0 \leq N \leq 1000$
• $1 \leq M \leq 1000$

Subtasks

Subtask #1 (100 points): Original constraints

Sample Input 1 

2
2 15
0 15

Sample Output 1 

30
0

Explanation

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.

Solution: