What is the increase/ (decrease) in Salary from the period 2017 to 2018?
{"Salary": {"2019": 896297, "2018": 927820, "2017": 903186}, "Bonus(1)": {"2019": 1280173, "2018": 3214578, "2017": 1044514}, "Charges and Non-cash Benefits(2)": {"2019": 5618382, "2018": 6971946, "2017": 1828814}, "Total(3)": {"2019": 7794852, "2018": 11114344, "2017": 3776514}}
salary_2018 = df["Salary"]["2018"]
salary_2017 = df["Salary"]["2017"]
answer = salary_2018 - salary_2017