while str = STDIN.gets
  n = str.split(" ")
  a = n[0].to_i
  b = n[1].to_i

  if a == 0 && b == 0
    break
  elsif b % 2 == 0
    for h in 1..a do
        for w in 1..b/2 do
        print "#."
        end
        print "\n"
        for w in 1..b/2 do
        print ".#"
        end
      print "\n"
    end
  else
    for h in 1..a do
        for w in 1..b/2 do
        print "#."
        end
        print "."
        print "\n"
        for w in 1..b/2 do
        print ".#"
        end
        print "."
        print "\n"
    end
    print "\n"
  end
    print "\n"
end
