Syntax error drivingdistance

I am new in sql and i am trying to get that works a subquery with pgr_drivingdistance and pgr_pointsaspolygon but i get the next error:

subqueries in FROM must to have an alias,for example, FROM (SELECT ...) [AS] foo.But in the code below the alias is di

Here is the code:

SELECT 1 as result,* FROM  pgr_pointsaspolygon('SELECT id, ST_X(the_geom) AS x, ST_Y(the_geom) AS y FROM ( 
     SELECT id,seq, id1 AS node, id2 AS edge, cost, the_geom FROM pgr_drivingdistance(
       ''''SELECT id, source, target, time_4 as cost FROM jaen'''',
          1, 15, false, false
      )as di
      JOIN jaen_vertices_pgr pt
      ON di.id1 = pt.id)');