h, w = gets.split.map(&:to_i)
Array.new(h){Array.new(w)}

while (h != 0 || w != 0)

h.times{|i| w.times{|j|
 if (i + j) % 2 == 0
 print "#"
else
 print "."
end 
}
puts ""
}
puts ""
  
 h, w = gets.split.map(&:to_i)
end

    
r="#" s='.' 
loop{ 
h,w=gets.split(" ").map(&:to_i) 
break if h==0 and w==0 
h.times{|i| w.times{|j| 
if (i+j)%2==0 
print("#{r}") 
else print("#{s}") 
end } 
puts"" } 
puts "" }
