Solve the programming task below in a Python markdown code block.
Chef's coding class is very famous in Chefland. 

This year X students joined his class and each student will require one chair to sit on. Chef already has Y chairs in his class. Determine the minimum number of new chairs Chef must buy so that every student is able to get one chair to sit on.

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

- The first line contains a single integer T — the number of test cases. Then the test cases follow.
- The first and only line of each test case contains two integers X and Y — the number of students in the class and the number of chairs Chef already has.

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

For each test case, output the minimum number of extra chairs Chef must buy so that every student gets one chair.

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

$1 ≤ T ≤ 1000$
$0 ≤ X, Y ≤ 100$

----- Sample Input 1 ------ 
4
20 14
41 41
35 0
50 100

----- Sample Output 1 ------ 
6
0
35
0

----- explanation 1 ------ 
- Test case 1: There are $20$ students in the class and Chef has $14$ chairs already. Therefore Chef must buy $6$ more chairs.
- Test case 2: There are $41$ students in the class and Chef already has exactly $41$ chairs. Therefore Chef does not need to buy any more chairs.
- Test case 3: There are $35$ students in the class and Chef has no chairs initially. Therefore Chef must buy $35$ chairs.