Can you spot the very obvious problem with this Sudoku magazine cover?

We're guessing the person who shot the photo for the front cover of "Sudoku Challenge Big 360 Puzzle Book" isn't actually much of a Sudoku fan.

There's a pretty obvious problem with the design, as not-even-that-eagle-eyed users of Imgur have pointed out.

Can you see it?

Scroll down for the big reveal...

Yes, they've written a '5' in a square that already has a '5' in it...

And, no, it's not photoshopped. This is a thing you can actually buy for four of your well-earned pounds.

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