Buy 2 Get 1 Free

 There is a sale going on in Chefland. For every 

2

items Chef pays for, he gets the third item for free (see sample explanations for more clarity).

It is given that the cost of 1

item is X rupees. Find the minimum money required by Chef to buy at least N

items.

Input Format

• First line will contain T

, number of test cases. Then the test cases follow.

Each test case contains of a single line of input, two integers N

and X

• .

Output Format

For each test case, output the minimum money required by Chef to buy at least N

items.

Constraints

• 1≤T≤1000

1≤N,X≤1000

Subtasks

• Subtask 1 (100 points): Original constraints.

Sample Input 1

4
3 4
4 2
5 3
6 1

Sample Output 1

8
6
12
4

Explanation

Test Case 1

: Chef wants 3 items where the cost of each item is 4 rupees. To minimise the expenditure, Chef can pay for 2 items and get the third item for free. This way, the total money required is 4⋅2=8

rupees.

Test Case 2

: To minimise the expenditure, Chef can do the following:

• Purchase 2

items for 2⋅2=4 rupees and get the third one free. Thus, the total number of items is 3

.

Purchase 1

item for 2⋅1=2 rupees. Now Chef has total 4

• items.

Thus, the minimum money required to buy 4

items is 4+2=6

rupees.

Test Case 3

: To minimise the expenditure, Chef can do the following:

• Purchase 2

items for 3⋅2=6 rupees and get the third one free. Thus, the total number of items is 3

.

Purchase 2

items for 3⋅2=6 rupees. Chef gets a third item for free. Now Chef has total 6 items which is greater than his requirement of 5

• items.

Chef wanted to buy at least 5

items. The minimum money required for that is 6+6=12

rupees.

Test Case 4

: To minimise the expenditure, Chef can do the following:

• Purchase 2

items for 1⋅2=2 rupees and get the third one free. Thus, the total number of items is 3

.

Purchase 2

items for 1⋅2=2 rupees and get the third one free.. Now Chef has total 6

• items.

Thus, the minimum money required to buy 6

items is 2+2=4 rupees.