Continuing the trend, this year too we present a 'Mystery' for you to solve!
You will be given two numbers: a and b; and you have to output a single integer. See the sample test cases for hints.

Input:

The first line of the input will contain an integer t : the number of test cases. Each of the next t lines contain 2 integer (a and b).

Output:

For each test case output a single integer that is answer for that test case. Don't forget to print each answer on separate lines!

Constraints:

1 ≤ t ≤ 100

0 ≤ a ≤ 1000

1 ≤ b ≤ 1000

SAMPLE INPUT
4
5 5
6 5
138 9
9 13

SAMPLE OUTPUT
0
1
3
9

Explanation

No explanation! Otherwise it won't be a mystery anymore ;)

见题面

见题面