# The Plank

You want to construct a long plank using smaller wooden pieces. There are three kinds of pieces of lengths $1$, $2$ and $3$ meters respectively, each which you have an unlimited number of. You can glue together several of the smaller pieces to create a longer plank. Figure 1: There are $7$ ways to glue together a $4$ meter plank.

If the plank should have length $n$ meters, in how many different ways can you glue pieces together to get a plank of the right length?

## Input

The first and only line of input contains an integer $n$ ($1 \le n \le 24$), the length of the new plank.

## Output

Output a single integer – the number of ways you can glue together a plank of length $n$ meters.

## Scoring

Your solution will be tested on a set of test groups, each worth a number of points. To get the points for a test group you need to solve all test cases in the test group. Your final score will be the maximum score of a single submission.

 Group Points Constraints $1$ $33$ $n \le 10$ $2$ $67$ No additional constraints
Sample Input 1 Sample Output 1
4

7