drop a check

Dear all...
I have created a check constraint without giving it a name..
now I have a check named "$25" in my table that I need to drop or
modify!!!
How can I do???
with names is simple

alter table tablename drop constraint constraintname;

but without name??   :-)

many thanks...

Ivan




-- 
Ivan Marchesini
Department of Civil and Environmental Engineering
University of Perugia
Via G. Duranti 93/a 
06125
Perugia (Italy)
e-mail: marchesini@unipg.it       ivan.marchesini@gmail.com
tel: +39(0)755853760
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