# ITP1_5_C: Print a Chessboard

def make_line(width, is_even)
  o = is_even ? 0 : 1
  width.times.inject('') do |line, n|
    line << ( (n + o).even? ? '#' : '.' )
  end
end

while true
  height, width = gets.split.map &:to_i
  break if height == 0 && width == 0

  even_line = make_line width, true
  odd_line  = make_line width, false

  (height / 2).times do
    puts even_line, odd_line
  end
  puts even_line if height.odd?
  puts
end