Print out the 5x5 example on a piece of paper, and then cut it a few times with scissors, then try to re-arrange it in a simpler configuration.

And others are easier. Kyus of approved katas won't be changed, so it's pointless to post suggestions to do it.

Why is it awful? It's actual requirement, to make your solution pass the tests for inputs larger than 1000 (or whatever the range is). If you cannot pass tests and get timeouts, it means your solution is not efficient enough and you have not solved the kata.

It's not a kata issue. You need to find better solution.