## 题目描述

Polycarp is reading a book consisting of $n$ pages numbered from $1$ to $n$ . Every time he finishes the page with the number divisible by $m$ , he writes down the last digit of this page number. For example, if $n=15$ and $m=5$ , pages divisible by $m$ are $5, 10, 15$ . Their last digits are $5, 0, 5$ correspondingly, their sum is $10$ . Your task is to calculate the sum of all digits Polycarp has written down. You have to answer $q$ independent queries.

## 输入输出格式

### 输入格式

The first line of the input contains one integer $q$ ( $1 \le q \le 1000$ ) — the number of queries. The following $q$ lines contain queries, one per line. Each query is given as two integers $n$ and $m$ ( $1 \le n, m \le 10^{16}$ ) — the number of pages in the book and required divisor, respectively.

### 输出格式

For each query print the answer for it — the sum of digits written down by Polycarp.

## 输入输出样例

### 输入样例 #1

7
1 1
10 1
100 3
1024 14
998244353 1337
123 144
1234312817382646 13


### 输出样例 #1

1
45
153
294
3359835
0
427262129093995