loop do

n = gets.split(" ")
h = n[0].to_i
w = n[1].to_i

if h == 0 && w == 0 then
    break
end

for i in 0..h-1

  for j in 0..w-1
 
    if (i + j) % 2 == 0 then 
      print "#"
    else
      print "." 
    end  

  end

print "\n"

end

print "\n"

end