pub fn main(world: World) -> Void raises {
    let a: i32 = 21
    let b: i32 = 6
    let ok: Bool = a + b == 27 && a - b == 15 && (a * b == 126 && a % b == 3)
    if ok {
        check world.out.write("integer arithmetic ok\n")
    }
}