Gym 100507C Zhenya moves from parents （线段树）

Zhenya moves from parents

题目链接：

http://acm.hust.edu.cn/vjudge/contest/126546#problem/C

Description

Zhenya moved from his parents’ home to study in other city. He didn’t take any cash with him, he only
took his father’s credit card with zero balance on it. Zhenya succeeds in studies at the University and
sometimes makes a little money on the side as a Maths tutor. As he makes his own money he spends only
it, and when it is over he uses the credit card. Every time he gets or spends money, he sends a letter to
his father, where he puts the following two things.

1. The date when it took place
2. The sum of earned or spent money
   Every time receiving a letter from Zhenya, his father calculates the debt on the credit card at the moment.
   But here a problem arises. The point is that Russian Post delivers letters in an order different to the one
   they were sent in.
   For example, in the first Zhenya’s letter the father read that on September 10 Zhenya spent one thousand
   rubles. He thought that his son had used the credit card, and now the debt is one thousand rubles. However
   the next day came a letter with the information that on September 9 Zhenya earned five hundred rubles.
   It means that half of the money he spent on September 10 was his own, and the debt on the credit card
   is just five hundred rubles.
   Help Zhenya’s father with his account management.
   

Input

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