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