What is the sum of the highest two long-lived assets in 2018?
{"United States": {"2019": 239511, "2018": 115869}, "Asia": {"2019": 301020, "2018": 12274}, "Europe": {"2019": 59925, "2018": 59936}, "Total": {"2019": 600456, "2018": 188079}}
us_assets = df["United States"]["2018"]
europe_assets = df["Europe"]["2018"]
assets = [us_assets, europe_assets]
assets.sort(reverse=True)
answer = assets[0] + assets[1]