C. Book Readingtime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputPolycarp 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.InputThe 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.OutputFor each query print the answer for it — the sum of digits written down by Polycarp.ExampleInput
7
1 1
10 1
100 3
1024 14
998244353 1337
123 144
1234312817382646 13
Output
1
45
153
294
3359835
0
427262129093995

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

1 45 153 294 3359835 0 427262129093995 
['math', '*1200']