CREATE TABLE table_204_649 (id DECIMAL, "rank" DECIMAL, "name" TEXT, "image" DECIMAL, "height\ ft  ( m ) " TEXT, "floors" DECIMAL, "year" DECIMAL, "notes" TEXT)

what is the difference in height between key tower and 55 public square
SELECT ABS((SELECT "height\nft (m)" FROM table_204_649 WHERE "name" = 'key tower') - (SELECT "height\nft (m)" FROM table_204_649 WHERE "name" = '55 public square'))
SELECT ABS((SELECT "height\nft (m)" FROM "table_204_649" WHERE "name" = 'key tower') - (SELECT "height\nft (m)" FROM "table_204_649" WHERE "name" = '55 public square'))