Задача K-based numbers

Описание

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 successive zeros.

For 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, containing N digits.

Формат входных данных

You may assume that 2 <= K <= 10; N >= 2; N + K <= 18. The numbers N and K in decimal notation separated by the line break.

Формат выходных данных

The result in decimal notation.