What was the change in the Gross increases for tax positions of prior years between 2018 and 2019?
{"Balance at beginning of fiscal year ": {"2019": 5841, "2018": 3115, "2017": 2799}, "Gross increases for tax positions of prior years": {"2019": 62, "2018": 21, "2017": 184}, "Gross increases for tax positions of the current year": {"2019": 39, "2018": 2893, "2017": 163}, "Gross decreases for tax positions of prior years ": {"2019": -3672, "2018": -188, "2017": -31}, "Balance at end of fiscal year": {"2019": 2270, "2018": 5841, "2017": 3115}}
gross_increases_2019 = df["Gross increases for tax positions of prior years"]["2019"]
gross_increases_2018 = df["Gross increases for tax positions of prior years"]["2018"]
answer = gross_increases_2019 - gross_increases_2018