B'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. The first line of the input contains one integer q ( 1 <= q <= 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 <= n, m <= 10^{16} ) -- the number of pages in the book and required divisor, respectively. For each query print the answer for it -- the sum of digits written down by Polycarp. '...