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- All Contests
- ProjectEuler+
- Project Euler #237: Tours on a 4 x n playing board

# Project Euler #237: Tours on a 4 x n playing board

# Project Euler #237: Tours on a 4 x n playing board

Contest ends in

_{This problem is a programming version of Problem 237 from projecteuler.net}

Let be the number of tours over an playing board such that:

- The tour starts in the top left corner;
- The tour consists of moves that are up, down, left, or right one square;
- The tour visits each square exactly once;
- The tour ends in the bottom left corner.

The following diagram shows one tour over a board:

Define = . It can be shown that and .

Given integers and , what is ?

Since the answer can be quite large, express your solution modulo .

**Input Format**

Each test file contains 2 lines. The first line contains and the second .

**Constraints**

- .
- .

**Output Format**

Print the integer value of your answer modulo .

**Sample Input 0**

```
4
3
```

**Sample Output 0**

```
6
```

**Explanation 0**

It is easily seen that and . Also, since the case has the following four solutions:

Thus .