Is Everyone Registered?

Field trip day! The teacher has the class list and the list of kids whose permission slips came back. 📋

You get the classlist and the registered names. If every classmate registered, print all set. Otherwise print the first classmate (in class-list order) who didn't.

Example:

Input: classlist = ["mia", "leo", "kai"], registered = ["leo", "mia", "kai"] Output: all set

Every classmate turns up somewhere in registered, so nothing is missing.

Input: classlist = ["mia", "leo", "kai"], registered = ["mia", "kai"] Output: leo

"leo" can't be found in registered, and he's the first classmate the search fails on.