CREATE TABLE table_name_77 (year INT, date VARCHAR, type VARCHAR, location VARCHAR)

What is the sum of Year with a Type of informal, and a Location with justus lipsius building, brussels, and a Date with 23 may?
SELECT SUM(year) FROM table_name_77 WHERE type = "informal" AND location = "justus lipsius building, brussels" AND date = "23 may"
SELECT SUM("year") FROM "table_name_77" WHERE "23 may" = "date" AND "informal" = "type" AND "justus lipsius building, brussels" = "location"