2 _ _ 9 _ _ _ _ _
_ _ _ _ _ _ _ 6 _
_ _ _ _ _ 1 _ _ _
5 _ 2 6 _ _ 4 _ 7
_ _ _ _ _ 4 1 _ _
_ _ _ _ 9 8 _ 2 3
_ _ _ _ _ 3 _ 8 _
_ _ 5 _ 1 _ _ _ _
_ _ 7 _ _ _ _ _ _


https://www.reddit.com/r/sudoku/comments/7q76ay/friend_tells_me_that_this_is_unsolvable_sudoku/