K-based numbers

http://acm.timus.ru/problem.aspx?space=1&num=1009

Time Limit: 1.0 second

Memory Limit: 1 000 KB

Let's consider K-based numbers, containing exactly N digits. We define a number to be valid if its K-based notation doesn't contain two successful zeroes.

Example:

1010230 is a valid 7-digit number
1000198 is not a valid number
0001235 is not a 7-digit number, it is a 4-digit number.

Given two numbers N and K, you are to calculate an amount of valid K based numbers, contaning N digits.

You may assume that 2 <= K <= 10; 2 <= N; 4 <= N+K <= 18.

1. Input

two decimal numbers N and K

2. Output

The result in decimal notation.

3. Sample Input

2
10

4. Sample Output

90