Guess a number!

1000ms

262144K

Description:

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".

Input:

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.

Output:

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).

Sample Input:

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

Sample Output:

Sample Input:

2
> 100 Y
< -100 Y

Sample Output:

Impossible

Informação

Provedor Codeforces

Código CF416A