import Control.Monad
import Data.Set
main=do
 n<-readLn
 a<-replicateM n getLine
 print(f n a empty)
  where f 0 _ s = size s
        f n a s = f(n-1)(tail a)(if(member(head a)s)then(delete(head a)s)else(insert(head a)s))