while(True):
  h, w = map(int, input().split())
  if h == 0 and w == 0:
    break
    
  for i in range(h):
    c =""
    for j in range(w):
      if (i+j)%2 == 0: 
        c += "#"
      else :
        c += "."
    print(c)
  print("")
