const GRID_STR: &'static str =
"08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48";

enum Direction {
	Up,
	Down,
	Left,
	Right,
	UpLeft,
	UpRight,
	DownLeft,
	DownRight
}

fn produce_valid_directions(grid_length: usize, coordinate: (usize, usize)) -> impl Iterator<Item=Direction> {
	let mut v = vec![];

	let has_up_clearance = coordinate.1 >= 3;
	let has_down_clearance = coordinate.1 <= (grid_length - 4);
	let has_left_clearance = coordinate.0 >= 3;
	let has_right_clearance = coordinate.0 <= (grid_length - 4);

	if has_up_clearance {
		v.push(Direction::Up);
		if has_left_clearance {
			v.push(Direction::UpLeft);
		}

		if has_right_clearance {
			v.push(Direction::UpRight);
		}
	}

	if has_down_clearance {
		v.push(Direction::Down);
		if has_left_clearance {
			v.push(Direction::DownLeft);
		}

		if has_right_clearance {
			v.push(Direction::DownRight);
		}
	}

	if has_left_clearance {
		v.push(Direction::Left);
	}

	if has_right_clearance {
		v.push(Direction::Right);
	}

	v.into_iter()
}

fn produce_grid_item_iterator(grid: &Vec<Vec<u64>>, coordinate: (usize, usize)) -> Box<dyn Iterator<Item=(u64, u64, u64, u64)>> {
	Box::new(produce_valid_directions(grid.len(), coordinate).map(|direction| match direction {
		Direction::Up => ((coordinate.0, coordinate.1), (coordinate.0, coordinate.1 - 1), (coordinate.0, coordinate.1 - 2), (coordinate.0, coordinate.1 - 3)),
		Direction::Down => ((coordinate.0, coordinate.1), (coordinate.0, coordinate.1 + 1), (coordinate.0, coordinate.1 + 2), (coordinate.0, coordinate.1 + 3)),
		Direction::Left => ((coordinate.0, coordinate.1), (coordinate.0 - 1, coordinate.1), (coordinate.0 - 2, coordinate.1), (coordinate.0 - 3, coordinate.1)),
		Direction::Right => ((coordinate.0, coordinate.1), (coordinate.0 + 1, coordinate.1), (coordinate.0 + 2, coordinate.1), (coordinate.0 + 3, coordinate.1)),
		Direction::UpLeft => ((coordinate.0, coordinate.1), (coordinate.0 - 1, coordinate.1 - 1), (coordinate.0 - 2, coordinate.1 - 2), (coordinate.0 - 3, coordinate.1 - 3)),
		Direction::UpRight => ((coordinate.0, coordinate.1), (coordinate.0 + 1, coordinate.1 - 1), (coordinate.0 + 2, coordinate.1 - 2), (coordinate.0 + 3, coordinate.1 - 3)),
		Direction::DownLeft => ((coordinate.0, coordinate.1), (coordinate.0 - 1, coordinate.1 + 1), (coordinate.0 - 2, coordinate.1 + 2), (coordinate.0 - 3, coordinate.1 + 3)),
		Direction::DownRight => ((coordinate.0, coordinate.1), (coordinate.0 + 1, coordinate.1 + 1), (coordinate.0 + 2, coordinate.1 + 2), (coordinate.0 + 3, coordinate.1 + 3)),
	})
	.map(|coordinates| (grid[(coordinates.0).1][(coordinates.0).0], grid[(coordinates.1).1][(coordinates.1).0], grid[(coordinates.2).1][(coordinates.2).0], grid[(coordinates.3).1][(coordinates.3).0]))
	.collect::<Vec<_>>().into_iter())
}

fn produce_grid_iterator(grid: &Vec<Vec<u64>>) -> Box<dyn Iterator<Item=(u64, u64, u64, u64)>> {
	let mut iter = produce_grid_item_iterator(grid, (0, 0));
	for i in 0..grid.len() {
		for j in 0..grid.len() {
			if (i == 0) && (j == 0) {
				continue;
			} else {
				let old_iter = std::mem::replace(&mut iter, Box::new(std::iter::once((0, 0, 0, 0))));
				let new_iter = Box::new(old_iter.chain(produce_grid_item_iterator(grid, (j, i))));
				std::mem::replace(&mut iter, new_iter);
			}
		}
	}
	iter
}

fn main() {
	let grid = GRID_STR.lines().map(|line| line.split(" ").map(|value| value.parse::<u64>().unwrap()).collect::<Vec<_>>()).collect::<Vec<_>>();
	println!("{:?}", produce_grid_iterator(&grid).map(|tup| tup.0 * tup.1 * tup.2 * tup.3).max());
}