You arrive m Ye Olde Magic Shoppe with some hard-earned gold to purchase wondrous and
unique magic items. There are n such items in the shop, each of them locked in a special magic
box. The i-th box costs ci gold pieces to buy, and contains an item worth vi gold pieces. The
costs and item values are known to you, as you have previously read, mastered, and memorized
Ye Olde Magic Catalogue.
A mortal, such as you, can safely carry only one magic item. You therefore aim to get the
most precious one. And obtain it you would, if not for a malicious, magical creature, known as
The Imp.
The Imp can cast a mischievous spell, which transforms the content of any magic box into
worthless dust. Of course, he will use the spell just after you buy a box, to make you pay for the
item and not get it. You are thus forced to buy another box, and then the next one_
The Imp has enough magic to cast the spell at most k times. He can, of course, refrain from
using it, allowing you to keep an item. You can walk away at any time, empty-handed (though
it would surely be a disgrace). However, if you get an item, you must keep it and leave the shop.
You aim to maximize your gain (the value of the acquired item minus all the expenses paid
previously), while The Imp wants to mimmize it. If both vou and the creature use the optimal
strategy, how much gold will vou earn?
T组询问。每组询问：
第一行有两个数字N,K，表示有N个物体，接下来每个物体有2个描述权值Vi, Ci，表示该物体的价值和价格。
商家很坑，他有K次机会使得你买完物品之后就立马让你买的该物品消失（但已经付了钱），而商家的目标
则是使得你的净收入尽量低。你可以无限量买东西，但最后只能带走一件物品，不过当然想要使得净收入尽
量高。在双方皆采取最佳策略的情况下，你最多能得到多少钱？（当然，你也可以什么都不买）
