All possible combinations for the first 4 letters of the alphabet?
I found this “diary” from when I was 6 years old, and it was one of those that you have to enter a code to open it. I don’t want to break it open, but I don’t remember the code.
It has four buttons with the first four letters of the alphabet, A,B,C and D.
What are all possible combinations using all four letters?
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