{-# OPTIONS_GHC -O2 -funbox-strict-fields #-}
{-# OPTIONS_GHC -fno-warn-unused-imports #-}
{-# OPTIONS_GHC -fno-warn-missing-signatures #-}
{-# OPTIONS_GHC -fno-warn-unused-binds #-}
{-# OPTIONS_GHC -fno-warn-incomplete-patterns #-}
{-# OPTIONS_GHC -fno-warn-name-shadowing #-}
{-# LANGUAGE OverloadedStrings #-}
-- {-# LANGUAGE FlexibleContexts #-}
-- {-# LANGUAGE MultiWayIf #-}
-- {-# LANGUAGE BangPatterns #-}
-- {-# LANGUAGE ViewPatterns #-}
-- {-# LANGUAGE TupleSections #-}

import           System.IO hiding (char8)
import           Control.Applicative
import           Control.Monad
import           Control.Monad.ST
import           Data.List hiding (find)
import           Data.Tuple
import           Data.Int
import           Data.Char
import           Data.Function (on, (&))
import           Data.Ord (comparing)
import           Data.Monoid (mappend)
import           Data.Array
-- import           Data.Array.Unboxed
-- import           Data.Array.IArray
import           Data.Array.ST
import           Data.Array.MArray
-- import           Data.Array.Unsafe
-- import           Data.Array.Base(unsafeRead, unsafeWrite)
-- import           Data.Array.IO
import           Data.Ix
import           Data.Maybe
-- import           Data.Monoid hiding ((<>))
import qualified Data.ByteString.Char8 as BS
import qualified Data.ByteString.Lazy.Char8 as BL
import           Data.ByteString.Builder
-- import           Data.Graph
-- import           Data.Vector.Unboxed ((//), (++), (!), (!?))
-- import qualified Data.Vector.Unboxed as U
-- import           Data.IntSet (IntSet)
-- import qualified Data.IntSet as IntSet
-- import           Data.IntMap.Strict (IntMap)
-- import qualified Data.IntMap.Strict as IntMap
import           Data.Sequence ((|>), (<|), (><),ViewR(..), ViewL(..), Seq)
import qualified Data.Sequence              as Seq
-- import           Data.Foldable (toList, minimumBy)
-- import           Debug.Trace

main = do
  n <- readInt1 <$> BS.getLine
  xys <- map readInt2 <$> replicateM n BS.getLine
  print . solve n $ unzip xys

-- solve :: Int -> ([Int], [Int]) -> Int
solve n (xs,ys) = sum $ kruskal n edges
  where
    edges = sortOn snd $ mkEdges xs ++ mkEdges ys
    mkEdges :: [Int] -> [Edge]
    mkEdges ns = zip [1..] ns
        & sortOn snd
        & \ms -> zipWith ((,) **** flip (-)) ms $ tail ms

(****) :: (a -> b -> c) -> (a' -> b' -> c') -> (a, a') -> (b, b') -> (c, c')
(****) f g (a, a') (b, b') = (f a b, g a' b')
infixr 3 ****

type Edge = ((Node, Node), Cost)
type Node = Int
type Cost = Int
kruskal :: Int -> [Edge] -> [Cost]
kruskal n es = runST $ do
  uf <- newUnionFind n
  k' uf es []
  where
    k' :: UnionFind s -> [Edge] -> [Cost] -> ST s [Cost]
    k' _ [] es' = return es'
    k' uf (((x,y),c):es) es' = do
      united <- find uf x y
      if united
        then k' uf es es'
        else unite uf x y >> k' uf es (c:es')


-- libs
-- http://jng.imagine27.com/index.php/2012-08-22-144618_purely-functional-data-structures-algorithms-union-find-haskell.html

-- Code from http://kwangyulseo.com/2014/01/30/implementing-union-find-algorithms-in-haskell/
data UnionFind s = UnionFind {
    ids:: STUArray s Int Int
  , szs:: STUArray s Int Int
  }

newUnionFind :: Int -> ST s (UnionFind s)
newUnionFind n = liftM2 UnionFind (newListArray (1, n) [1..n]) (newArray (1, n) 1)

find :: UnionFind s -> Int -> Int -> ST s Bool
find uf p q = liftM2 (==) (root uf p) (root uf q)

root :: UnionFind s -> Int -> ST s Int
root uf i = do
    ix <- readArray (ids uf) i
    if ix /= i
        then do
            gpid <- readArray (ids uf) ix
            writeArray (ids uf) i gpid
            root uf ix
        else return i

unite :: UnionFind s -> Int -> Int -> ST s ()
unite uf p q = do
    i <- root uf p
    j <- root uf q
    szi <- readArray (szs uf) i
    szj <- readArray (szs uf) j
    if szi < szj
        then do
            writeArray (ids uf) i j
            writeArray (szs uf) j (szi + szj)
        else do
            writeArray (ids uf) j i
            writeArray (szs uf) i (szj + szi)

--  --  --  --  --  --  --  --  --  --  --  --  --  --  --  --  --  --  --  --

getInt1 :: IO Int
getInt1 = readInt1 <$> BS.getLine

getInt2 :: IO (Int, Int)
getInt2 = readInt2 <$> BS.getLine

getInt3 :: IO (Int, Int, Int)
getInt3 = readInt3 <$> BS.getLine

getInts :: IO [Int]
getInts = readInts <$> BS.getLine

getIntN :: Int -> IO [Int]
getIntN n = map readInt1 <$> replicateM n BS.getLine

format :: Show a => Maybe a -> IO ()
format Nothing = putStrLn "NO"
format (Just a) = putStrLn "YES" >> print a

-- [1,2,3] -> 1 2 3
putInts :: [Int] -> IO ()
-- putInts [] = return ()
-- putInts xs = BL.putStrLn . toLazyByteString . foldl1 mappend . intersperse (char8 ' ') $ map intDec xs
putInts = putStrLn . unwords . map show

readInt1 :: BS.ByteString -> Int
readInt1 = fst . fromJust . BS.readInt

readInt2 :: BS.ByteString -> (Int,Int)
readInt2 = toTuple . readInts

readInt3 :: BS.ByteString -> (Int,Int,Int)
readInt3 = toTriple . readInts

readInts :: BS.ByteString -> [Int]
readInts =  map readInt1 . BS.words

readInt641 :: BS.ByteString -> Int64
readInt641 = fromIntegral . fst . fromJust . BS.readInteger

readInt642 :: BS.ByteString -> (Int64,Int64)
readInt642 = toTuple . readInt64s

readInt643 :: BS.ByteString -> (Int64,Int64,Int64)
readInt643 = toTriple . readInt64s

readInt64s :: BS.ByteString -> [Int64]
readInt64s =  map readInt641 . BS.words

readInteger1 :: BS.ByteString -> Integer
readInteger1 = fst . fromJust . BS.readInteger

readInteger2 :: BS.ByteString -> (Integer,Integer)
readInteger2 = toTuple . readIntegers

readInteger3 :: BS.ByteString -> (Integer,Integer,Integer)
readInteger3 = toTriple . readIntegers

readIntegers :: BS.ByteString -> [Integer]
readIntegers =  map readInteger1 . BS.words

toTuple :: [a] -> (a, a)
toTuple [x, y] = (x, y)

toTriple :: [a] -> (a, a, a)
toTriple [x, y, z] =(x, y, z)

fromTuple :: (a, a) -> [a]
fromTuple (x, y) = [x, y]

fromTriple :: (a, a, a) -> [a]
fromTriple (x, y, z) = [x, y, z]

-- if not applying, use "id"

applyTuple :: (a -> a') -> (b -> b') -> (a, b) -> (a', b')
applyTuple f g (x, y) = (f x, g y)

applyTriple :: (a -> a') -> (b -> b') -> (c -> c') -> (a, b, c) -> (a', b', c')
applyTriple f g h (x, y, z) = (f x, g y, h z)

-- @since 4.8.0.0
sortOn' :: Ord b => (a -> b) -> [a] -> [a]
sortOn' f =
  map snd . sortBy (comparing fst) . map (\x -> let y = f x in y `seq` (y, x))


Measured memory_bytes: 88444