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 ""
end
  
 h, w = gets.split.map(&:to_i)
end

    

