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