What was the change in Cost of cloud and software in 2019 from 2018?
{"Cost of cloud and software": {"2019": 138, "2018": 78, "2017": 115}, "Cost of services": {"2019": 246, "2018": 142, "2017": 158}, "Research and development": {"2019": 429, "2018": 210, "2017": 269}, "Sales and marketing": {"2019": 562, "2018": 312, "2017": 442}, "General and administration": {"2019": 461, "2018": 88, "2017": 135}, "Share-based payment expenses": {"2019": 1835, "2018": 830, "2017": 1120}, "Thereof cash-settled share-based payments": {"2019": 1664, "2018": 674, "2017": 963}, "Thereof equity-settled share-based payments": {"2019": 171, "2018": 156, "2017": 157}}
cost_of_cloud_and_software_2019 = df["Cost of cloud and software"]["2019"]
cost_of_cloud_and_software_2018 = df["Cost of cloud and software"]["2018"]
answer = cost_of_cloud_and_software_2019 - cost_of_cloud_and_software_2018