def row_sharp(w)
  for i in 1..w
    if i%2 == 0
      print "."
    else
      print "#"
    end
  end
end

def row_dot(w)
  for i in 1..w
    if i%2 == 0
      print "#"
    else
      print "."
    end
  end
end


input_values = []
while true
  input_value  = gets.chomp.split.map(&:to_i)
  if input_value == [0,0]
    break
  end
  input_values.push(input_value)
end

num_of_chessboard = (input_values.length)

for i in 0..(num_of_chessboard-1)
    h = input_values[i][0]
    w = input_values[i][1]
    for j in 0..(h-1)
      rows = []
      if j%2 == 0
        rows.push(row_sharp(w))
      else
        rows.push(row_dot(w))
      end
      rows.delete_at(-1)
      puts rows.join('\n')
    end
    puts"\n"
end