Berland National Library has recently been built in the capital of Berland. In addition, in the library you can take any of the collected works of Berland leaders, the library has a reading room.
Today was the pilot launch of an automated reading room visitors' accounting system! The scanner of the system is installed at the entrance to the reading room. It records the events of the form "reader entered room", "reader left room". Every reader is assigned aregistration number during the registration procedure at the library — it's a unique integer from 1 to 106. Thus, the system logs events of two forms:
- "+ ri" — the reader with registration number ri entered the room;
- "- ri" — the reader with registration number ri left the room.
The first launch of the system was a success, it functioned for some period of time, and, at the time of its launch and at the time of its shutdown, the reading room may already have visitors.
Significant funds of the budget of Berland have been spent on the design and installation of the system. Therefore, some of the citizens of the capital now demand to explain the need for this system and the benefits that its implementation will bring. Now, the developers of the system need to urgently come up with reasons for its existence.
Help the system developers to find the minimum possible capacity of the reading room (in visitors) using the log of the system available to you.
The first line contains a positive integer n (1 ≤ n ≤ 100) — the number of records in the system log. Next follow n events from the system journal in the order in which the were made. Each event was written on a single line and looks as "+ ri" or "- ri", where ri is an integer from 1 to 106, the registration number of the visitor (that is, distinct visitors always have distinct registration numbers).
It is guaranteed that the log is not contradictory, that is, for every visitor the types of any of his two consecutive events are distinct. Before starting the system, and after stopping the room may possibly contain visitors.
Print a single integer — the minimum possible capacity of the reading room.
6 + 12001 - 12001 - 1 - 1200 + 1 + 7
3
2 - 1 - 2
2
2 + 1 - 1
1
In the first sample test, the system log will ensure that at some point in the reading room were visitors with registration numbers 1, 1200and 12001. More people were not in the room at the same time based on the log. Therefore, the answer to the test is 3.
题目大意：给出图书馆的访客记录系统的一段时间的日志，每条记录表示有某个人进入或离开图书馆。在这段日志开始前、结束后图书馆里都可能有人。求这段日志记录的时间内图书馆内最大的访客人数。
StartCount为日志开始前的人数，Count为当前人数减去StartCount。按顺序处理日志，对于某条记录，如果是有人进入，就递增Count，如果有人出去且之前记录了他在图书馆内，就递减Count，如果之前没有记录，就递增StartCount并递减Count。结果就是Count+StartCount的最大值。
代码在此。
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