Santa is sitting in his office at the North Pole, planning the best route for delivering packages to all the children, when one of the elves comes through the door. "Santa, I was working my way through the wishlists from the children when I came across this rather peculiar letter" said the elf. "Oh, what is special about it?" Santa replied. The elf handed over the envelope. "This letter doesn't contain a wishlist, but something that looks more like a challenge for you. And there even is a coin to pay you for it." "Interesting" Santa mumbled. "It seems like someone found out that I can't resist a challenge. I still have some time before Christmas so I might just as well spend a little time on this letter." Santa unfolded the letter and started looking at it.
Santa picks up the coin and flips it between his fingers. "I really hope this coin brings some luck. The task looks rather difficult, and the coin seems too old to be accepted as payment."
"I am sure you will figure this out" the elf said on the way out of the office. "I have never seen a challenge you can't beat."
