def rand_coord(board, used=None):
    if used is None:
        used = []
    ind = choice([arg for arg in board[1].flatten().argsort() if arg not in used])
    used.append(ind)
    if board[1].flatten()[ind] == 1:
        return rand_coord(board, used)
    else:
        return divmod(ind, board.shape[2])

def rand_coord(board, used=[]):
    ind = choice([arg for arg in board[1].flatten().argsort() if arg not in used])
    used.append(ind)
    if board[1].flatten()[ind] == 1:
        return rand_coord(board, used)
    else:
        return divmod(ind, board.shape[2])