{-# LANGUAGE ViewPatterns #-}
import qualified Data.Sequence as Sq
import Data.Sequence (ViewL(..),ViewR(..),(><),(<|),(|>),Seq)
import Data.List

f::[String]->[(Int,Int,Int)]
f []=[]
f (s:ss)=let (x:y:c:[])=map read (words s)::[Int]
         in (x,y,c):f ss

left :: Seq a -> a
left (Sq.viewl -> (l :< _)) = l

left2 :: Seq a -> Seq a
left2 (Sq.viewl -> (_ :< ls)) = ls

f3::Sq.Seq (Int,Int)->Sq.Seq (Int,Int)->Sq.Seq (Int,Int)
f3 old now
   |Sq.null old=now
   |otherwise=let a=left old
                  old2=left2 old
              in f3 old2 (now |> a)

f2::Int->Int->Int->Int->[(Int,Int,Int)]->Sq.Seq (Int,Int)->Sq.Seq (Int,Int)->Int
f2 _ ans _ _ [] _ _=ans
f2 x ans nowC nowC2 xs3@((x2,y2,c2):xs2) old now
         |x<x2=f2 x2 ans 0 0 xs3 (f3 old now) (Sq.empty :: Sq.Seq (Int,Int))
         |Sq.null old=let c4=max (nowC+c2) nowC2
                      in f2 x (max ans c4) nowC c4 xs2 old (now |> (y2,c4))
         |otherwise=let (y3,c3)=left old
                        old2=left2 old
                        c5=(max nowC c3)
                        c6=(max nowC2 (c5+c2))
                    in if y2 > y3 then f2 x (max ans c6) c5 c6 xs3 old2 (now |> (y3,c5))
                                  else f2 x (max ans c5) nowC nowC2 xs2 old (now |> (y2,(max (nowC+c2) nowC2)))

f4::(Int,Int,Int)->Int
f4 (a,_,_)=a

f5::[(Int,Int,Int)]->[(Int,Int,Int)]
f5  (x:[])=[x]
f5 ((x,y,c):(x1,y1,c1):xs)
   |x==x1&& y==y1=f5 ((x1,y1,c1):xs)
   |otherwise=(x,y,c):f5 ((x1,y1,c1):xs)

main = do
       e<-getLine
       es<-getContents
       let q=(Sq.fromList [(0::Int,0::Int)])
           xs=f5 $ sort $ f $ lines es
       print $ f2 (f4 (head xs)) 0 0 0 xs q q