square=['#','.']
while True:
  HW=input().split()
  HW=[int(x) for x in HW]
  if HW[0] == 0: break
  for i in range(HW[0]):
    for j in range(HW[1]):
      print(square[(i+1+j+1)%2], end='')
    print('')
  print('')