x = gets()
y = x.split()
h = y[0].to_i
w = y[1].to_i

until h == 0 && w ==0
 i = 1
 while i <= h
  if i % 2 == 1
   if w % 2 ==1
    k = "#" * ((w + 1) / 2)
    s = k.split("")
    puts s.join(".")
   else
    puts "#." * (w / 2)
   end
   i += 1
  else
   if w % 2 ==1
    k = "." * ((w + 1) / 2)
    s = k.split("")
    puts s.join("#")
   else
    puts ".#" * (w / 2)
   end
   i += 1
  end
 end
 puts ""
 x = gets()
 y = x.split()
 h = y[0].to_i
 w = y[1].to_i
end 

