package main

import (
	"fmt"
)

type Desk struct{ Capacity, Used int }

func (d *Desk) Accept(amount int) bool {
	if d == nil || d.Capacity < 0 || d.Used < 0 || d.Used > d.Capacity || amount <= 0 || amount > d.Capacity-d.Used {
		return false
	}
	d.Used += amount
	return true
}

func main() {
	desk := Desk{Capacity: 5, Used: 2}
	fmt.Println(desk.Accept(2), desk.Used)
	fmt.Println(desk.Accept(2), desk.Used)
}