I'd say they're head and last.

why are h and l used as variable names? do they stand for something?

Not to be mean, but I'm not sure this is the best solution. There have been more concise ways of doing this given below, and using if conditions and returns in the same line makes me uncomfortable.

Hell, when I was creating my code, I thought I was the smartest...
And it turns out that 6 years ago there were people much smarter than me

the or is so smart use

This deserves more upvotes! I see so many solutions that are literally summing lists of numbers when you can simply do it in constant time with a bit of arithmetics.

alas

where can I find my solution without commenting on a solution?

nice work, very smart :)

I had to make a solution like this too, because of the long data type. I had originally had good, concise solution, but had to use a brute force solution like this.

I hate this abuse :D

They are two parameters of a lambda expression

I thought something like that after finished my solution

What are "r" and "i"? they are not declared...

This is much shorted and easier to read.
I feel dumb.