What was the difference in the fair value for U.S. Treasury and government debt securities between Level 1 and Level 2?
{"Cash": {"Total": 2216, "Level 1": 2216, "Level 2": "$  \u2014"}, "Corporate bonds": {"Total": 1353, "Level 1": "\u2014", "Level 2": 1353}, "U.S. Treasury and government debt securities": {"Total": 213, "Level 1": 131, "Level 2": 82}, "Certificates of deposit": {"Total": 117, "Level 1": "\u2014", "Level 2": 117}, "Total cash, cash equivalents and short-term investments": {"Total": 3899, "Level 1": 2347, "Level 2": 1552}, "Other items: -- Mutual funds (1)": {"Total": 6, "Level 1": 6, "Level 2": "$  \u2014"}, "Other items: -- Mutual funds (2)": {"Total": 29, "Level 1": 29, "Level 2": "$  \u2014"}, "Other items: -- Foreign currency exchange contracts assets (1)": {"Total": 4, "Level 1": "$  \u2014", "Level 2": 4}, "Other items: -- Foreign currency exchange contracts liabilities (3)": {"Total": -1, "Level 1": "$  \u2014", "Level 2": -1}}
level_1 = df["U.S. Treasury and government debt securities"]["Level 1"]
level_2 = df["U.S. Treasury and government debt securities"]["Level 2"]
answer = level_1 - level_2