CREATE TABLE table_204_593 (id DECIMAL, "year" TEXT, "chairperson" TEXT)

who held the position longer , t.v sivaraopantulu or l. suryalingam ?
SELECT "chairperson" FROM table_204_593 WHERE "chairperson" IN ('t.v. sivaraopantulu', 'l. suryalingam') ORDER BY "year" - "year" DESC LIMIT 1
SELECT "chairperson" FROM "table_204_593" WHERE "chairperson" IN ('t.v. sivaraopantulu', 'l. suryalingam') ORDER BY "year" - "year" DESC NULLS LAST LIMIT 1