def printChessBoard(h,w)
  h.to_i.times{|i|
    black = i % 2
    w.to_i.times{|j|
      print (black == 0)? "#" : "."
      black = (black + 1) % 2
    }
    print "\n"
  }
end

while true
  h,w = gets.chomp.split
  break if h.to_i == 0 && w.to_i == 0
  printChessBoard(h,w)
  puts "\n"
end