Think about it like a loop. If you are going to start at a value, and count up to it, then if you start above it then you're going to halt right away. Luckily there is a third part to slicing that is a step. Normally, it's 1, but you can set it to any integer you want, including negative ones. Also, they're all optional so you can just use the third and let the first and second default to start and end.
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