#102477. [BZOJ 2477] Biggest Number

You have a maze with obstacles and non-zero digits in it：

You can start from any square，walk in the maze，and finally stop at some square．Each step，you may only walk into one of the four neighbouring squares （up，down，left，right） and you cannot walk into obstacles or walk into a square more than once．When you finish，you can get a number by writing down the digits you encounter in the same order as you meet them．For example，you can get numbers etc．The biggest number you can get is ，shown in the picture above．
Your task is to find the biggest number you can get．

There will be at most test cases．Each test begins with two integers and ，the number of rows and columns of the maze．The next rows represent the maze．Each line contains exactly characters （without leading or trailing spaces），each of them will be either # or one of the nine non-zero digits．There will be at least one non-obstacle squares （i.e. squares with a non-zero digit in it） in the maze．The input is terminated by a test case with ，you should not process it．

For each test case，print the biggest number you can find，on a single line．

样例输入 #1

3 7
##9784#
##123##
##45##
0 0

样例输出 #1

791452384

的数据满足：。

湖南省第六届大学生计算机程序设计竞赛