export fn _start() noreturn {
    const y = fibonacci(7);
    exit(y - 21);
}

fn fibonacci(n: usize) callconv(.Inline) usize {
    if (n <= 2) return n;
    return fibonacci(n - 2) + fibonacci(n - 1);
}

fn exit(code: usize) noreturn {
    asm volatile ("syscall"
        :
        : [number] "{rax}" (231),
          [arg1] "{rdi}" (code)
        : "rcx", "r11", "memory"
    );
    unreachable;
}