The cunning chef wants to keep the burnt side of his pancakes down.
To do that, he can only use the flip operation on his stack of pancakes, i.e., he inserts his spatula at some point in between the stack of the pancakes and flips the ones above the spatula, like this:
The chef, being cunning, will make sure that he'll fix any stack of pancakes in the least number of flips he can.
For which one of these three stacks of pancakes would he require the most number of flips?
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Each flip reduces the number of borders (between pancakes of different orientation) by one. (+ 1 extra flip if the bottom pancake is burnt side up.
There are 4 borders in A, no borders in B, (+1 flip), and 2 borders in C (+1 flip).
So, the number of flips for each stack is:
So, A will take the most flips.