Aider works best with Claude 3.7 Sonnet, DeepSeek R1 & Chat V3, OpenAI o1, o3-mini & GPT-4o, but can connect to almost any LLM, including local models.

Optical illusions play tricks on our brains, forcing us to look closer and think harder. Today’s challenge is no different—hidden among several pairs of 25 and 28, a lone "22" lurks. Can you find it?

EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, Scotland EH9 3FJ, U.K.