Guess a number!

题意翻译

小 A 和小 B 正在玩一个猜数游戏。 小 A 给出一个数 $x$，并让小 B 问下面四个问题中的一个： - 这个数是否大于等于 $x$？ - 这个数是否大于 $x$？ - 这个数是否小于等于 $x$？ - 这个数是否小于 $x$？ 小 A 会对小 B 提出的每个问题作出回答，试根据这些条件判断任意**符合条件**的**一个**数，或者这些条件相互矛盾。 $-2\times 10^9\leqslant x\leqslant 2\times 10^9$。

题目描述

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".

输入输出格式

输入格式

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 $ -10^{9}<=x<=10^{9} $ . The answer is an English letter "Y" (for "yes") or "N" (for "no"). Consequtive elements in lines are separated by a single space.

输出格式

Print any of such integers $ y $ , that the answers to all the queries are correct. The printed number $ y $ must meet the inequation $ -2·10^{9}<=y<=2·10^{9} $ . If there are many answers, print any of them. If such value doesn't exist, print word "Impossible" (without the quotes).

输入输出样例

输入样例 #1

4
>= 1 Y
< 3 N
<= -3 N
> 55 N

输出样例 #1

17

输入样例 #2

2
> 100 Y
< -100 Y

输出样例 #2

Impossible