CF416A.Guess a number!

A TV show called "Guess a number!" is gathering popularity. The whole Berland, the old and the young, are watching the show.

The rules are simple. The host thinks of an integer y and the participants guess it by asking questions to the host. There are four types of acceptable questions:

• Is it true that y is strictly larger than number x?
• Is it true that y is strictly smaller than number x?
• Is it true that y is larger than or equal to number x?
• Is it true that y is smaller than or equal to number x?

On each question the host answers truthfully, "yes" or "no".

Given the sequence of questions and answers, find any integer value of y that meets the criteria of all answers. If there isn't such value, print "Impossible".

一档名为“猜数字！”的电视节目正日益流行，整个贝尔兰，无论老少，都在收看该节目。

游戏规则很简单：主持人会想好一个整数 $y$，参与者通过向主持人提问来猜测这个数字。允许提出的问题共有四种类型：

• $y$ 是否严格大于数字 $x$？
• $y$ 是否严格小于数字 $x$？
• $y$ 是否大于或等于数字 $x$？
• $y$ 是否小于或等于数字 $x$？

对于每个问题，主持人都会如实回答“是”或“否”。

给定一系列问题及其答案，请找出任意一个满足所有答案条件的整数 $y$。若不存在这样的整数，则输出 "Impossible"。

The first line of the input contains a single integer n (1 ≤ n ≤ 10000) — the number of questions (and answers). Next n lines each contain one question and one answer to it. The format of each line is like that: "sign x answer", where the sign is:

• ">" (for the first type queries),
• "<" (for the second type queries),
• ">=" (for the third type queries),
• "<=" (for the fourth type queries).

All values of x are integer and meet the inequation  - 109 ≤ x ≤ 109. The answer is an English letter "Y" (for "yes") or "N" (for "no").

Consequtive elements in lines are separated by a single space.

输入的第一行包含一个整数 $n$（$1 \leq n \leq 10000$）—— 表示问题（及对应答案）的数量。接下来的 $n$ 行，每行包含一个问题及其对应答案。每行的格式为：“sign x answer”，其中 sign 是：

• “>”（表示第一类查询），
• “<”（表示第二类查询），
• “>=”（表示第三类查询），
• “<=”（表示第四类查询）。

所有 $x$ 的取值均为整数，且满足不等式 $-10^9 \leq x \leq 10^9$。answer 是一个英文字母：“Y”（表示“是”）或 “N”（表示“否”）。

每行中相邻元素之间以单个空格分隔。

Print any of such integers y, that the answers to all the queries are correct. The printed number y must meet the inequation  - 2·109 ≤ y ≤ 2·109. If there are many answers, print any of them. If such value doesn't exist, print word "Impossible" (without the quotes).

输出任意一个满足所有查询答案正确的整数 $y$。输出的数字 $y$ 必须满足不等式 $-2\cdot10^9 \leq y \leq 2\cdot10^9$。若存在多个解，输出其中任意一个即可。若不存在这样的值，则输出单词 "Impossible"（不带引号）。