Table schema:
CREATE TABLE table_name_37 (population INTEGER, density__inhabitants_km_2__ VARCHAR, altitude__mslm_ VARCHAR, city VARCHAR)

Question: What is the lowest population of alessandria where the altitude is less than 197 and density is less than 461.8?
SQL: SELECT MIN(population) FROM table_name_37 WHERE altitude__mslm_ < 197 AND city = "alessandria" AND density__inhabitants_km_2__ < 461.8