while 1:
  H , W = map( int , raw_input().split() )
  if ( H , W ) == ( 0 , 0 ):
    break
  for k in range(H):
    if k%2 == 0 and W%2 == 0:
      print "#." * ( W/2 )
    elif k%2 == 0 and W%2 == 1:
      print "#." * ( W/2 ) + "#"
    elif k%2 == 0 and W%2 == 0:
      print ".#" * ( W/2 )
    elif k%2 == 0 and W%2 == 1:
      print ".#" * ( W/2 ) + "."
    print ''