#ITP1-ITP1_5_C
while True:
  h,w = (input().split())
  h = int(h)
  w = int(w)
  if h == 0 and w == 0:
    break
  for a in range(1,h+1):
    if a%2 == 1:
      print("#."*(w//2),"#"*(w%2),sep="")
    else:
      print(".#"*(w//2),"."*(w%2),sep="")
  print("")
