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.
-----Input-----
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.
-----Output-----
For each query print the answer for it — the sum of digits written down by Polycarp.
-----Example-----
Input
7
1 1
10 1
100 3
1024 14
998244353 1337
123 144
1234312817382646 13
Output
1
45
153
294
3359835
0
427262129093995
import math
tst = int(input())
for _ in range(tst):
    b, a = list(map(int, input().split()))
    b //= a
    cnt = b // 10
    sum = 0
    for i in range(1, 11):
        sum += (a * i) % 10
    sum *= cnt
    for i in range(1, b % 10 + 1):
        sum += (a * i) % 10
    print(sum)


import math
tst = int(input())
for _ in range(tst):
    b, a = list(map(int, input().split()))
    b //= a
    cnt = b // 10
    sum = 0
    for i in range(1, 11):
        sum += (a * i) % 10
    sum *= cnt
    for i in range(1, b % 10 + 1):
        sum += (a * i) % 10
    print(sum)

