Can u help me gus. I have task: “write a function that takes three arrays in a tuple (array1, array2, array3) and returns the longest common

subsequence of the arrays”. I dont have idea how to do .

```
let longest n = fun a1 a2 a3 ->
let a = Array.make (Array.length a1 + Array.length a2 + Array.length a3) a1.(0)) in
for
a;;
```