Indian Institute of Technology, Madras: Arindama Singh's "Cantor's Little Theorem"
Read this paper. Spend some time studying the proof of Cantor's Theorem on pages 3 and 4. Even though the proof is quite brief, this idea is new to you, and therefore is likely to be harder to understand.
Click https://mat.iitm.ac.in/home/asingh/public_html/papers/cantor.pdf link to open resource.