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)+'#')
  else:
   if W % 2 == 0:
    print ('.#'*(W//2))
   else:
    print ('.#'*(W//2)+'.')
 print ''