Everyone Who Showed Up

Two field-trip buses, two messy name lists, some kids listed on both. How many kids actually came? 🚌

You get bus1 and bus2 name lists. Print the total number of DIFFERENT kids across both buses.

Example:

Input: bus1 = ["mia", "leo"], bus2 = ["leo", "kai", "ana"] Output: 4

Merging the sets gives {"mia", "leo", "kai", "ana"} — "leo" counts once even though he's on both buses, for 4 different kids.