step sudo
    | isSolved sudo = [sudo]
    | hasSolution (possibleNumsForBlankPos sudo) && (uniqueNumForBlankPos (possibleNumsForBlankPos sudo)) /= [] = take 1 [insertElem sudo (a,b) c |
    a <- [0..8], b <- [0..8], c <- possibleNumsOnPos sudo (a,b) ,(length (possibleNumsOnPos sudo (a,b)) == 1), isBlank sudo (a,b)]
    | otherwise = take (length (possibleNumsOnPos sudo ((blankPositions sudo) !! 0)))
    [insertElem sudo (a,b) c | a <- [0..8], b <- [0..8], c <- possibleNumsOnPos sudo (a,b), isBlank sudo (a,b)]