let A0_width = 841 mm
let A0_height = 1189 mm

fn paper_width_A(n: Scalar) -> Length =
    floor(A0_width / 2^(n / 2))

fn paper_height_A(n: Scalar) -> Length =
    floor(A0_height / 2^(n / 2))

fn paper_area_A(n: Scalar) -> Area =
    paper_width_A(n) × paper_height_A(n)

assert_eq(paper_width_A(3), 297 mm)
assert_eq(paper_height_A(3), 420 mm)

assert_eq(paper_width_A(4), 210 mm)
assert_eq(paper_height_A(4), 297 mm)

assert_eq(paper_width_A(5), 148 mm)
assert_eq(paper_height_A(5), 210 mm)