human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: Rank, Railway Station, Annual entry/exit (millions) 2011–12, Annual interchanges (millions) 2011–12, Total Passengers (millions) 2011–12, Location, Main Services, Number of Platforms
###Question: What is the lowest rank of Gatwick Airport? 
gpt
SELECT MIN Rank FROM table WHERE Railway Station = Gatwick Airport