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Time limit 2000/4000/4000/4000 ms. Memory limit 65000/65000/65000/65000 Kb. 
Difficulty Alpha
  
A chessboard pattern is a pattern that satisfies the following conditions: 
 
• The pattern has a rectangular shape. 
• The pattern contains only the characters '.' (a dot) and 'X' (an uppercase letter X). 
• No two symbols that are horizontally or vertically adjacent are the same. 
• The symbol in the lower left corner of the pattern is '.' (a dot). 
 
You are given two numbers. N is a number of rows and M is a
number of columns. Write a program that generates the chessboard pattern
with these dimensions, and outputs it. 
 
Input 
The first line contains two numbers N and M
(1 ≤ N ≤ 50, 1 ≤ M ≤ 50) separated by a whitespace. 
Output 
Output should contain N lines each containing M symbols that
correspond to the generated pattern. Specifically, the first character
of the last row of the output represents the lower left corner (see example 1). 
 
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Input 1
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Input 2
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Input 3
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8 8 
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3 1 
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1 20 
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Output 1
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Output 2
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Output 3
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X.X.X.X. 
.X.X.X.X 
X.X.X.X. 
.X.X.X.X 
X.X.X.X. 
.X.X.X.X 
X.X.X.X. 
.X.X.X.X 
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. 
X 
. 
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.X.X.X.X.X.X.X.X.X.X 
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Для отправки решений необходимо выполнить вход.
  
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