Kata

Challenge: The lockdown has ended and a group of friends want to take their families to the fairground.

They all want to ride on the main attraction: the ferris wheel!

                   __  __
               __ [_|]'_|] __
              [_|].-'-_-_'-._]
            _.'.'-.-''   '-.-'__
           [_|]-.'.  '   ' .'.-_]
          _/ /_/ '.'. ' ' .  .' -_
         [_|]_'    '.'_'_. .'  '._]
          |_|_| = = (.-_o) = = :-_'
         [_|] _    .//\/_\.    .-_]
           \_\_\ .'//_//_\\'. .-.
           [_|]_`./.-/.-.-.\_'-_]
             '.'.-'-//__.\.\\.'
              [_|]-/.-_ .-[_\\
               // // [_|]  \.\\
         _____//_//_________\.\\_____                                wheeeee!

However, there are some conditions:

• Each cabin on the ferris wheel can hold up to 3 people, and each cabin must have at least 1 adult.

• They all want to ride at the same time and don't want to leave anybody out, otherwise they wont ride at all.

• Let's pretend the ferris wheel has an infinite number of cabins available.

Task:

Given two integers as arguments (number of adults, number of children) return the mininum number of cabins needed for the group to ride, otherwise return -1 if they decide not to ride at all.