This is an optional assignment and can be a little tricky. The Fibonacci sequence is an infinite sequence of numbers that starts with 0 and 1 and then adds the previous number with the current to get the next number.

```
round 1:
0 <-- previous
1 <-- current
1 <-- new
```

```
round 2:
0
1 <-- previous
1 <-- current
2 <-- new
```

This sequence has many real-world applications and is even a naturally occurring phenomenon in plants and animals. This assignment will not introduce you to any real-world applications but is a fun puzzle to solve that will allow you to flex your new loop-building muscles.

### Setup

Fork the following repository and clone your copy (if you haven't already for this lesson).

Open `fibonacci.py`

in your text editor.

### Requirements

#### General

- ask the user if they want to:
`1) calculate the nth Fibonacci number 2) calculate the last Fibonacci number less than or equal to n 3) quit`

#### Loops

- solve the selected option using loops. Each option lends itself more to a certain loop type. It is your job to find out which one goes with which

#### Tips

- the first 10 Fibonacci numbers are:
`0 1 1 2 3 5 8 13 21 34`

- an efficient algorithm will require you to swap the values of two variables.
You can do this using a temporary variable. Since this is a bit tricky, I will
provide you with the part you will need.
`temp = current current += previous previous = temp`