hard1 :: Puzzle
hard1 = [
    1, 0, 0, 0, 0, 0, 0, 0, 2,
    0, 9, 0, 4, 0, 0, 0, 5, 0,
    0, 0, 6, 0, 0, 0, 7, 0, 0,
    0, 5, 0, 9, 0, 3, 0, 0, 0,
    0, 0, 0, 0, 7, 0, 0, 0, 0,
    0, 0, 0, 8, 5, 0, 0, 4, 0,
    7, 0, 0, 0, 0, 0, 6, 0, 0,
    0, 3, 0, 0, 0, 9, 0, 8, 0,
    0, 0, 2, 0, 0, 0, 0, 0, 1 ]
hard1 :: Puzzle
hard1 = [
    1, 0, 0, 0, 0, 0, 0, 0, 2,
    0, 9, 0, 4, 0, 0, 0, 5, 0,
    0, 0, 6, 0, 0, 0, 7, 0, 0,
    0, 5, 0, 9, 0, 3, 0, 0, 0,
    0, 0, 0, 0, 7, 0, 0, 0, 0,
    0, 0, 0, 8, 5, 0, 0, 4, 0,
    7, 0, 0, 0, 0, 0, 6, 0, 0,
    0, 3, 0, 0, 0, 9, 0, 8, 0,
    0, 0, 2, 0, 0, 0, 0, 0, 1 ]
hard1 = [
    1, 0, 0, 0, 0, 0, 0, 0, 2,
    0, 9, 0, 4, 0, 0, 0, 5, 0,
    0, 0, 6, 0, 0, 0, 7, 0, 0,
    0, 5, 0, 9, 0, 3, 0, 0, 0,
    0, 0, 0, 0, 7, 0, 0, 0, 0,
    0, 0, 0, 8, 5, 0, 0, 4, 0,
    7, 0, 0, 0, 0, 0, 6, 0, 0,
    0, 3, 0, 0, 0, 9, 0, 8, 0,
    0, 0, 2, 0, 0, 0, 0, 0, 1 ]