What is the change in the cash and cash equivalents between 2019 and 2018?
{"Cash and cash equivalents": {"December 31, 2019": 19505, "December 31, 2018": 18017}, "Restricted cash": {"December 31, 2019": 1205, "December 31, 2018": 1444}, "Total cash, cash equivalents and restricted cash in the consolidated statements of cash flows": {"December 31, 2019": 20710, "December 31, 2018": 19461}}
cash_2019 = df["Cash and cash equivalents"]["December 31, 2019"]
cash_2018 = df["Cash and cash equivalents"]["December 31, 2018"]
answer = cash_2019 - cash_2018