Joe works in a maze. Unfortunately, portions of the maze have caught on fire, and the owner of the maze neglected to create a fire escape plan. Help Joe escape the maze. Given Joe’s location in the maze and which squares of the maze are on fire, you must determine whether Joe can exit the maze before the fire reaches him, and how fast he can do it. Joe and the fire each move one square per minute, vertically or horizontally (not diagonally). The fire spreads all four directions from each square that is on fire. Joe may exit the maze from any square that borders the edge of the maze. Neither Joe nor the fire may enter a square that is occupied by a wall.

 

Input

The first line of input contains a single integer, the number of test cases to follow. The first line of each test case contains the two integers R and C, separated by spaces, with 1 ≤ R, C ≤ 1000. The

following R lines of the test case each contain one row of the maze. Each of these lines contains exactly

C characters, and each of these characters is one of:

 

• #, a wall

 

• ., a passable square

 

• J, Joe’s initial position in the maze, which is a passable square

 

• F, a square that is on fire

 

There will be exactly one J in each test case.

 

Output

For each test case, output a single line containing ‘IMPOSSIBLE’ if Joe cannot exit the maze before the fire reaches him, or an integer giving the earliest time Joe can safely exit the maze, in minutes.

 

Sample Input

2

4 4

####

#JF#

#..#

#..#

3 3

###

#J.

#.F

 

Sample Output

3

IMPOSSIBLE

 

题目类型：BFS

算法分析：同时扩展Joe可以走的位置和着火的区域(这里分别是将两个扩展的时间同步来实现的)，注意图中可以存在多个Fire的地方！！！

 

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