What is the total stock based compensation amount between 2017 to 2019?
{"Stock-based compensation by type of award: -- Stock options": {"2019": 648, "2018": 1353, "2017": 2705}, "Stock-based compensation by type of award: -- Stock awards": {"2019": 14882, "2018": 10445, "2017": 11421}, "Stock-based compensation by type of award: -- Employee stock purchase rights(1)": {"2019": 999, "2018": 5240, "2017": 3077}, "Stock-based compensation by type of award: -- Total": {"2019": 16529, "2018": 17038, "2017": 17203}, "Stock-based compensation by category of expense: -- Cost of revenue": {"2019": 1500, "2018": 1602, "2017": 1362}, "Stock-based compensation by category of expense: -- Sales and marketing": {"2019": 5765, "2018": 5667, "2017": 6075}, "Stock-based compensation by category of expense: -- Research and development": {"2019": 6039, "2018": 6631, "2017": 6343}, "Stock-based compensation by category of expense: -- General and administrative": {"2019": 3225, "2018": 3138, "2017": 3423}, "Stock-based compensation by category of expense: -- Total": {"2019": 16529, "2018": 17038, "2017": 17203}}
total_2019 = df["Stock-based compensation by type of award: -- Total"]["2019"]
total_2018 = df["Stock-based compensation by type of award: -- Total"]["2018"]
total_2017 = df["Stock-based compensation by type of award: -- Total"]["2017"]
answer = total_2019 + total_2018 + total_2017