CREATE TABLE table_203_56 (id DECIMAL, "star" TEXT, "start\ year" DECIMAL, "end\ year" DECIMAL, "maximum\ year" DECIMAL, "maximum\ magnitude" DECIMAL, "distance at\ maximum  ( ly ) " DECIMAL, "current\ distance" DECIMAL, "current\ magnitude" DECIMAL)

how much farther -lrb- in ly -rrb- is epsilon canis majoris than zeta sagittarii ?
SELECT (SELECT "distance at\nmaximum (ly)" FROM table_203_56 WHERE "star" = 'epsilon canis majoris') - (SELECT "distance at\nmaximum (ly)" FROM table_203_56 WHERE "star" = 'zeta sagittarii')
SELECT (SELECT "distance at\nmaximum (ly)" FROM "table_203_56" WHERE "star" = 'epsilon canis majoris') - (SELECT "distance at\nmaximum (ly)" FROM "table_203_56" WHERE "star" = 'zeta sagittarii')