for i in range(3000):
  h,w=(int(a) for a in input().split())
  if w==0 and h==0:
    break
  for j in range(h):
    for k in range(w):
      if (j+k)%2==0:
        print("#",sep="",end="")
      else:
         print(".",sep="",end="")
    print("")
  print("")
