fun first_permutation(idx: Int) do
		for i in [0..p.length[ do p[i] = i

		for i in [0..count.length[.reverse_iterator do
			var d = idx / fact[i]
			count[i] = d
			idx = idx % fact[i]

			p.copy_to(0, i+1, pp, 0)

			for j in [0..i] do p[j] = if j + d <= i then pp[j+d] else pp[j+d-i-1]
		end
	end