What is the difference between the balance in September 2018 for contract assets and contract liabilities?
{"Assets -- Contract assets(1)": {"Balance as of August 31, 2018": "$\u2014", "Adjustments due to adoption of ASU 2014-09": 591616, "Balance as of September 1, 2018": 591616}, "Assets -- Inventories, net(1)": {"Balance as of August 31, 2018": 3457706, "Adjustments due to adoption of ASU 2014-09": -461271, "Balance as of September 1, 2018": 2996435}, "Assets -- Prepaid expenses and other current assets(1)(2)": {"Balance as of August 31, 2018": 1141000, "Adjustments due to adoption of ASU 2014-09": -37271, "Balance as of September 1, 2018": 1103729}, "Assets -- Deferred income taxes(1)(2)": {"Balance as of August 31, 2018": 218252, "Adjustments due to adoption of ASU 2014-09": -8325, "Balance as of September 1, 2018": 209927}, "Liabilities -- Contract liabilities(2)(3)": {"Balance as of August 31, 2018": "$\u2014", "Adjustments due to adoption of ASU 2014-09": 690142, "Balance as of September 1, 2018": 690142}, "Liabilities -- Deferred income(2)(3)(4)": {"Balance as of August 31, 2018": 691365, "Adjustments due to adoption of ASU 2014-09": -691365, "Balance as of September 1, 2018": "$\u2014"}, "Liabilities -- Other accrued expenses(3)(4)": {"Balance as of August 31, 2018": 1000979, "Adjustments due to adoption of ASU 2014-09": 40392, "Balance as of September 1, 2018": 1041371}, "Liabilities -- Deferred income taxes(1)": {"Balance as of August 31, 2018": 114385, "Adjustments due to adoption of ASU 2014-09": 2977, "Balance as of September 1, 2018": 117362}, "Equity -- Retained earnings(1)(2)": {"Balance as of August 31, 2018": 1760097, "Adjustments due to adoption of ASU 2014-09": 42602, "Balance as of September 1, 2018": 1802699}}
contract_liabilities_2018_09 = df["Liabilities -- Contract liabilities(2)(3)"]["Adjustments due to adoption of ASU 2014-09"]
contract_assets_2018_09 = df["Assets -- Contract assets(1)"]["Adjustments due to adoption of ASU 2014-09"]
answer = contract_liabilities_2018_09 - contract_assets_2018_09