union step = Step : i32 * i32 * i32

inl open_step (x : i32) : step =
    if x > 2 then Step (x, x + 1, x + 2) else Step (0, 1, 2)

let walk (x : i32) : i32 =
    match open_step x with
    | Step (a, b, c) => a + b * c

inl main () : i32 =
    inl ~n = 5i32
    walk n + walk (n - 4)