Sum of digits

http://acm.timus.ru/problem.aspx?space=1&num=1206

Time Limit: 1.0 second

Memory Limit: 1 000 KB

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:

S(A+B) = S(A) + S(B)

1. Input

The input file contains a single positive integer K, 0 < K <= 50. Output

You should output the number of pairs of К-digit numbers A and B to satisfy the above equality. Counting that number you should be aware of the following:

1. Numbers A and B should not have leading zeroes
2. 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.

2. Sample Input

2

3. Sample Output

1980

Problem Author: Leonid Volkov

Problem Source: USU Internal Contest, March 2002