I am trying to solve this challenge on HackerRank:
<https://www.hackerrank.com/challenges/30-operators?h_r=next-challenge&h_v=zen>

the way I tried to read the stdin is this:

`let input = readline()!`

However, the input consists of three lines, e.g. 

```
12.00
20
8

```

How do I get all three lines, ideally in some separated way so that I can cast them to their respective types?