문제 설명 Make a program that filters a list of strings and returns a list with only your friends name in it. If a name has exactly 4 letters in it, you can be sure that it has to be a friend of yours! Otherwise, you can be sure he's not... Ex: Input = ["Ryan", "Kieran", "Jason", "Yous"], Output = ["Ryan", "Yous"] i.e. friend ["Ryan", "Kieran", "Mark"] `shouldBe` ["Ryan", "Mark"] Note: keep the orig..