use of dba_hist views

I have the following query and hope to get the database growth through dba_hist views. But I am getting some errors. Not sure how to modify that.

select b.tsname tablespace_name, max(b.used_size_mb) cur_used_size_mb, round(AVG(inc_used_size_mb),2)avg_increas_mb
from (
select a.days, a.tsname, used_size_mb, used_size_mb - LAG(used_size_mb,1) OVER ( PARTITION BY a.tsname ORDER BY a.tsname, a.days) inc_used_size_mb
from (
select TO_CHAR(sp.begin_interval_time, 'MM_DD_YYYY') days, ts.tsname,
max(round((tsu.tablespace_usedsize*dt.block_size)/(1024*1024),2)) used_size_mb