What country that is a member of the International Centre for Settlement of Investment Disputes has the most GDP?
select ?ent where { ?ent wdt:P31 wd:Q6256 . ?ent wdt:P2131 ?obj . ?ent wdt:P463 wd:Q899770 } ORDER BY DESC(?obj)LIMIT 5 
country: Q6256 international centre for settlement of investment disputes: Q899770