What is the change in the Fair value through other comprehensive income from 2017 to 2018?
{"Non-current assets": {"2019 m": 48, "2018 m": "-", "2017 m": "-"}, "Fair value through other comprehensive income": {"2019 m": "-", "2018 m": 46, "2017 m": 37}, "Available-for-sale": {"2019 m": 6, "2018 m": 7, "2017 m": 7}, "Fair value through profit or loss": {"2019 m": 54, "2018 m": 53, "2017 m": 44}, "Current assets -- Fair value through other comprehensive income": {"2019 m": "-", "2018 m": "-", "2017 m": "-"}, "Current assets -- Available-for-sale": {"2019 m": "-", "2018 m": 2575, "2017 m": 1437}, "Current assets -- Investments held at amortised cost": {"2019 m": 3214, "2018 m": "-", "2017 m": "-"}, "Current assets -- Loans and receivables": {"2019 m": "-", "2018 m": 447, "2017 m": 83}, "Current assets -- ": {"2019 m": 3214, "2018 m": 3022, "2017 m": 1520}}
fair_value_2018 = df["Fair value through other comprehensive income"]["2018 m"]
fair_value_2017 = df["Fair value through other comprehensive income"]["2017 m"]
answer = fair_value_2018 - fair_value_2017