CREATE TABLE table_203_731 (id DECIMAL, "pos." TEXT, "city" TEXT, "population\ ( ab ) " DECIMAL, "surface\ ( km2 ) " DECIMAL, "density\ ( ab/km2 ) " DECIMAL, "altitude\ ( mslm ) " DECIMAL)

what is the highest city in terms of altitude ?
SELECT "city" FROM table_203_731 ORDER BY "altitude\n(mslm)" DESC LIMIT 1
SELECT "city" FROM "table_203_731" ORDER BY "altitude\n(mslm)" DESC NULLS LAST LIMIT 1