Identity number which appears exactly once.

Similar Problems:

A chess knight can move as indicated in the chess diagram below:

This time, we place our chess knight on any numbered key of a phone pad (indicated above), and the knight makes N-1 hops. Each hop must be from one key to another numbered key.

Each time it lands on a key (including the initial placement of the knight), it presses the number of that key, pressing N digits total.

How many distinct numbers can you dial in this manner?

Since the answer may be large, output the answer modulo 10^9 + 7.

Example 1:

Input: 1 Output: 10

Example 2:

Input: 2 Output: 20

Example 3:

Input: 3 Output: 46

Note:

- 1 <= N <= 5000

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

- Solution: XXX

**General Thinkings:**

**Key Observations:**

**Walk Through Testdata**

// Blog link: https://code.dennyzhang.com/knight-dialer