Rehan and Checkpoints

Rehan is tracking a numbered sequence of checkpoints in a long training route, labeled from \(1\) to \(N\)

During the training, rehan only pays attention to checkpoints whose numbers are divisible by \(M\). Whenever he reaches such a checkpoint, he record the last digit of that checkpoint number as a small note.

For instance, if \(N = 27\) and \(M = 9\) the relevant checkpoints are \(9, 18\) and \(27\). The recorded last digits are \(9, 8\) and \(7\), and their total is \(24\).

Your task is to determine the sum of all recorded digits.

You are given \(Q\) independent queries, and for each query, compute the required sum.

Input Format

First line contains an integer \(Q\). Next \(Q\) lines contains queries, one per line with two integers \(N\) and \(M\).

Output Format

For each query print the sum of recorded digits.

Constraints

• \[1 ≤ Q ≤ 1000\]
• \[1 ≤ N, M ≤ 10^{16}\]

Sample Input 0

1
27 9

Sample Output 0

24