use std::cell::Cell;
use std::cell::RefCell;
use std::rc::Rc;
use std::rc::Weak;

fn a(
    k: i32,
    x1: &dyn Fn() -> i32,
    x2: &dyn Fn() -> i32,
    x3: &dyn Fn() -> i32,
    x4: &dyn Fn() -> i32,
    x5: &dyn Fn() -> i32,
) -> i32 {
    let weak_holder: Rc<RefCell<Weak<dyn Fn() -> i32>>> =
        Rc::new(RefCell::new(Weak::<fn() -> i32>::new()));
    let weak_holder2 = weak_holder.clone();
    let k_holder = Cell::new(k);
    let b: Rc<dyn Fn() -> i32> = Rc::new(move || {
        let b = weak_holder2.borrow().upgrade().unwrap();
        k_holder.set(k_holder.get() - 1);
        return a(k_holder.get(), &*b, x1, x2, x3, x4);
    });
    weak_holder.replace(Rc::downgrade(&b));

    return if k <= 0 { x4() + x5() } else { b() };
}

pub fn main() {
    println!("{}", a(10, &|| 1, &|| -1, &|| -1, &|| 1, &|| 0));
}