Let us denote the sum of digits of the number N by S(N). In this problem, we want you to determine, how often the following equality holds:
The input contains a single integer K, 2 ≤ K ≤ 50.
You should output the number of pairs of K
-digit numbers A
to satisfy the above equality. Counting that number you should be aware of the following:
- numbers A and B should not have leading zeroes;
- while counting the total number of pairs, the order of numbers A and B matters, thus, for instance, (12, 26) and (26, 12) are different pairs that satisfy the conditions of the problem.
Problem Author: Leonid Volkov
Problem Source: USU Internal Contest, March 2002