trigger udatetrig on contact (after update)

{list<lead> plist=new list<lead>();

for(contact a:trigger.new)

{

for(lead c:[select Name from lead where contactid=:a.id])

{

c.lastname=a.lastname;c.

contactid=a.id;plist.add(c);

}

}

update plist;

}

I have an Error as "" Error: Compile Error: Invalid field contactid for SObject Lead at line 9 column 1""

please solve my problem

Thanks in Advance.