What is the percentage change in the outstanding number of shares at the beginning of the period from 2018 to 2019?
{"Outstanding at the beginning of the period": {"2019 NUMBER": 768806, "2018 NUMBER": 3384696}, "Granted during the period": {"2019 NUMBER": "-", "2018 NUMBER": "-"}, "Forfeited during the period": {"2019 NUMBER": -768806, "2018 NUMBER": -2615890}, "Exercised during the period": {"2019 NUMBER": "-", "2018 NUMBER": "-"}, "Outstanding at the end of the period": {"2019 NUMBER": "-", "2018 NUMBER": 768806}}
outstanding_2019 = df["Outstanding at the beginning of the period"]["2019 NUMBER"]
outstanding_2018 = df["Outstanding at the beginning of the period"]["2018 NUMBER"]
answer = (outstanding_2019 - outstanding_2018) / outstanding_2018 * 100.0