while true
  h,w = gets.chomp.split(" ").map &:to_i
  break if w == 0 and h == 0

  h.times { |i|
   w.times { |j|
     if (i+j)%2 == 0
       print "#"
     else
       print "."
     end
   }
   puts
  }

  puts
end