Well, it's both dumb and smart: it's smart in the sense that it recognized the pattern in the first place, and it's dumb that it made such a silly error (and missed obvious ways to make it shorter).
This is the problem with these systems: "roughly correct, but not quite, and ends up with the wrong answer". In the case of a simple program that's easy to spot and correct for (assuming you already know to program well – I fear for students) but in more soft topics that's a lot harder. When I see people post "GPT-4 summarized the post as [...]" it may be correct, or it may have missed one vital paragraph or piece of nuance which would drastically alter the argument.