原题样例是有空行的：

输入：

3
3 3
XOX
XXX
XOX

3 5
XXXXX
XXXOO
XXXOO

4 4
XXXX
OOOO
XXXX
OOOO

输出：

O
X
X

原题目下有一评论：

nadstratosfer: 2018-02-21 15:41:57

Take care of random blanklines in input when solving with Python. Great problem and not easy at all, my solution needed a not-so-basic algo as well as a certain assumption that I can't prove. Generating many testcases and analyzing them helped.

意味， Python 使用者注意输入中的随机空行。