What was the total percentage change in the cash conversion cycle between 2017 and 2019?
{"(in days) -- Three Months Ended": {"April 26, 2019": 26, "April 27, 2018": 27, "April 28, 2017": 28}, "(in days) -- Days sales outstanding (1)": {"April 26, 2019": 70, "April 27, 2018": 58, "April 28, 2017": 45}, "(in days) -- Days inventory outstanding (2)": {"April 26, 2019": 21, "April 27, 2018": 18, "April 28, 2017": 26}, "(in days) -- Days payables outstanding (3)": {"April 26, 2019": -87, "April 27, 2018": -90, "April 28, 2017": -56}, "(in days) -- Cash conversion cycle (4)": {"April 26, 2019": 3, "April 27, 2018": -14, "April 28, 2017": 15}}
cash_conversion_cycle_2019 = df["(in days) -- Cash conversion cycle (4)"]["April 26, 2019"]
cash_conversion_cycle_2017 = df["(in days) -- Cash conversion cycle (4)"]["April 28, 2017"]
answer = (cash_conversion_cycle_2019 - cash_conversion_cycle_2017) / cash_conversion_cycle_2017 * 100.0