fn recurse(const x y : int, a : array(byte, [x, y]), px py : int) : int
[
	if px = x - 2, py = y - 1 then
		return 1;
	var req_dir := a[px, py];
	a[px, py] := 'O';
	var max_r := -1;
	for d in "^>v<" do [
		var dx, dy := 0, 0;
		if d = '^' then dx, dy := 0, -1;
		if d = '>' then dx, dy := 1, 0;
		if d = 'v' then dx, dy := 0, 1;
		if d = '<' then dx, dy := -1, 0;
		if req_dir <> '.', req_dir <> d then
			continue;
		if a[px + dx, py + dy] = '#' or a[px + dx, py + dy] = 'O' then
			continue;
		var r := recurse(x, y, a, px + dx, py + dy);
		max_r := max(max_r, r);
	]
	if max_r = -1 then
		return -1;
	return max_r + 1;
]

fn main
[
	var lines := list_break_to_lines(read_lazy(h[0]));
	const x := len(lines[0]);
	const y := len(lines);
	var a := list_to_array([x, y], list_join(lines, ""));
	a[1, 0] := '#';
	var result := recurse(x, y, a, 1, 1);
	write(h[1], ntos(result) + nl);
]