Solve the programming task below in a Python markdown code block.
There are N children and Chef wants to give them 1 candy each. Chef already has X candies with him. To buy the rest, he visits a candy shop. In the shop, packets containing exactly 4 candies are available.

Determine the minimum number of candy packets Chef must buy so that he is able to give 1 candy to each of the N children.

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

- The first line of input will contain a single integer T, denoting the number of test cases.
- The first and only line of each test case contains two integers N and X — the number of children and the number of candies Chef already has.

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

For each test case, output the minimum number of candy packets Chef must buy so that he is able to give 1 candy to each of the N children.

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

$1 ≤ T ≤ 1000$
$1 ≤ N, X ≤ 100$

----- Sample Input 1 ------ 
4
20 12
10 100
10 9
20 9

----- Sample Output 1 ------ 
2
0
1
3

----- explanation 1 ------ 
Test Case $1$: Chef must buy $2$ more packets after which he will have $20$ candies which will be enough to distribute $1$ candy to each of the $20$ children.

Test Case $2$: Chef does not need to buy more packets since he already has $100$ candies which are enough to distribute $1$ candy to each of the $10$ children.

Test Case $3$: Chef must buy $1$ more packet after which he will have $13$ candies which will be enough to distribute $1$ candy to each of the $10$ children.

Test Case $4$: Chef must buy $3$ more packets after which he will have $21$ candies which will be enough to distribute $1$ candy to each of the $20$ children.