What is the difference in payment for United States and Foreign for 2020?
{"": {"United States": "(in thousands)", "Foreign": ""}, "2020": {"United States": 8027, "Foreign": 1237}, "2021": {"United States": 8416, "Foreign": 985}, "2022": {"United States": 9163, "Foreign": 982}, "2023": {"United States": 9785, "Foreign": 1258}, "2024": {"United States": 10558, "Foreign": 1098}, "2025-2029": {"United States": 59665, "Foreign": 6129}}
us_2020 = df["2020"]["United States"]
foreign_2020 = df["2020"]["Foreign"]
answer = us_2020 - foreign_2020