What is the mistake

Question

https://code.sololearn.com/cJ23g4K4pKx7/?ref=app
https://code.sololearn.com/cJ23g4K4pKx7/?ref=app

Answer 1

You forgot to
1. Declare the "diff" variable
2. Pass "diff" as the second argument of printf

Here's a code bit that fixes the issue in your code:
https://code.sololearn.com/c47w2J2y82Ri/?ref=app