while True:
 h,w=map(int,input().split())
 if h==0:break
 for i in range(h):
  if i%2==0:print("".join(['#' if i%2==0 else '.' for i in range(w)]))
  else:print("".join(['.' if i%2==0 else '#' for i in range(w)]))
 print()