fn main
[
	var lines := list_break_to_lines(read_lazy(h[0]));
	var safe := 0;
	for line in lines do [
		var levels := map(list_break_whitespace(line), ston);
		var direction := 0;
		for i := 1 to len(levels) do [
			if i = 1 then [
				direction := sgn(levels[i - 1] - levels[i]);
				if direction = 0 then
					goto fail;
			]
			if direction <> sgn(levels[i - 1] - levels[i]) or abs(levels[i - 1] - levels[i]) > 3 then
				goto fail;
		]
		safe += 1;
fail:
	]
	write(h[1], ntos(safe) + nl);
]