def difference(dataset, interval=1):
    """
    Differencing time series according to difference_order/interval
    dataset:
        type:list, 
        Desc: list contaning timeseries values
    interval: 
        type:integers
        Desc: Differencing order
    """
    def do_diff(dataset):
        diff = list()
        for i in range(1, len(dataset)):
            value = dataset[i] - dataset[i - 1]
            diff.append(value)
        return diff

    diff_list = dataset
    last_obs_value = []
    for _ in range(1, interval + 1):
        last_obs_value.append(diff_list[0])
        diff_list = do_diff(diff_list)
    return diff_list, last_obs_value