Please explain for me on this code...line by line please ...its confussing!...i did not understand the math applied

Question

https://code.sololearn.com/c0zB1vzwUUo6/?ref=app

Answer 1

Please still i have the problem on how the printf have been excitedLexus Collins

Answer 2

How will i know the length of the output i this example? Lexus Collins