What is the increase / (decrease) in the Class A Voting shares from 2018 to 2019?
{"Common shares outstanding 1 -- Class A Voting": {"2019": 111154811, "2018": 111155637}, "Common shares outstanding 1 -- Class B Non-Voting": {"2019": 393770507, "2018": 403657038}, "Common shares outstanding 1 -- Total common shares": {"2019": 504925318, "2018": 514812675}, "Non-Voting Shares -- Outstanding options": {"2019": 3154795, "2018": 2719612}, "Non-Voting Shares -- Outstanding options exercisable": {"2019": 993645, "2018": 1059590}}
class_a_voting_shares_2019 = df["Common shares outstanding 1 -- Class A Voting"]["2019"]
class_a_voting_shares_2018 = df["Common shares outstanding 1 -- Class A Voting"]["2018"]
answer = class_a_voting_shares_2019 - class_a_voting_shares_2018