What is the change in the Impairment of long-term investments between 2017 and 2018?
{"Asset impairment charges": {"2019": 10837, "2018": 58166, "2017": 0}, "Goodwill impairment charge": {"2019": 25700, "2018": 13466, "2017": 0}, "Impairment of long-term investments": {"2019": 651, "2018": 15487, "2017": 165290}}
impairment_of_longterm_investments_2018 = df["Impairment of long-term investments"]["2018"]
impairment_of_longterm_investments_2017 = df["Impairment of long-term investments"]["2017"]
answer = impairment_of_longterm_investments_2018 - impairment_of_longterm_investments_2017