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.

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

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-----
Output the lexicographically smallest word in the crossword.

-----Examples-----
Sample Input 1:
4 4
luka
o#a#
kula
i#a#
Sample Output 1:
kala

Sample Input 2:
4 4
luka
o#a#
kula
i#as
Sample Output 2:
as

Difficulty: introductory

Starter code:

Solutions: