I am given the following input:

```
[[['3', '7'], ['9', '17']], [['1', '5'], ['10', '20']], [['0', '6'], ['12', '19']]]

```

Each sub-array consists of one or more elements`[['3', '7'], ['9', '17']]` means that this function1 is growing between x = 3 and x = 7, the same function1 is also growing between x=9 and x = 17.
Another function2 is growing between x=1 and x=5, and the same function2 is growing between x=10 and x=20.

This can be seen in a better formatted way here:

```
[['3', '7'], ['9', '17']]
[['1', '5'], ['10', '20']]
[['0', '6'], ['12', '19']]

```

I need to find a way to compute the max growth interval of all the 3 functions together. In this case the solution is from x = 12 to x = 17, because 17-12 = 5 is bigger than any other possible combination.

another solution is x =3 to x =5, but since is not the maximal, this is not the correct solution

Is there a pythonic way to find this?

Until now i tried to compute it for this specific case, without success.

This is the simplest case I am given, and it's only one case out of many. 
My problem is that i can't find the correct way to compare the element of the sublists, in order to get where all the functions are growing in the same interval...