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Have a look at this 4x4 Sudoku. Can you figure out which number goes in the blue frame?

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Continue to play the quiz afterwards
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Interesting fact:

Ever hear of Cicada 3301? It’s allegedly a secret organization of hackers and codebreakers who recruit new members via the posting of extremely difficult puzzles and challenges online. Solve one of them and it’s likely you could join their ranks.

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