Little Ivica solves crossword puzzles every day. In case you haven't seen one, a crossword puzzle starts on a grid of \(R \times C\) squares, each of which is either empty or blocked. The player's task is to write words in consecutive empty squares vertically (top down) or horizontally (left to right).

Ivica's sister has a strange habit of looking at crosswords Ivica has finished solving, and finding the lexicographically smallest word in it. She only considers words at least \(2\) characters long.

Write a program that, given a crossword puzzle, finds that word.

The first line contains two integers \(R\) and \(C\) (\(2 \le R, C \le 20\)), the number of rows and columns in the crossword.

Each of the following \(R\) lines contains a string of \(C\) characters. Each of those characters is either a lowercase letter of the English alphabet, or the character # representing a blocked square.

The input will be such that a solution will always exist.

Output the lexicographically smallest word in the crossword.

riseoj 작성

출처 COCI 2007/2008 Contest 2