user: Question: What is total number of years that has genre of First-person shooter?
Columns: ['Year', 'Game', 'Genre', 'Platform(s)', 'Developer(s)']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [2003.0, 'Star Wars: Knights of the Old Republic', '( Role-Playing Game ) Turn-Based', 'Windows , Xbox', 'Bioware']
SQL:

assistant: SELECT SUM("Year") FROM "Table" WHERE "Genre" = 'First-person shooter';