package main

import (
	"bufio"
	"container/heap"
	"fmt"
	"io"
	"os"
	"sort"
	"strconv"
)

var (
	readString func() string
	stdout     *bufio.Writer
)

func init() {
	readString = newReadString(os.Stdin)
	stdout = bufio.NewWriter(os.Stdout)
}

func newReadString(ior io.Reader) func() string {
	r := bufio.NewScanner(ior)
	r.Buffer(make([]byte, 1024), int(1e+11))
	r.Split(bufio.ScanWords)

	return func() string {
		if !r.Scan() {
			panic("Scan failed")
		}
		return r.Text()
	}
}

func readInt() int {
	return int(readInt64())
}

func readInt64() int64 {
	i, err := strconv.ParseInt(readString(), 0, 64)
	if err != nil {
		panic(err.Error())
	}
	return i
}

func readIntSlice(n int) []int {
	b := make([]int, n)
	for i := 0; i < n; i++ {
		b[i] = readInt()
	}
	return b
}

func readLengthAndSlice() []int {
	n := readInt()
	return readIntSlice(n)
}

func printf(f string, args ...interface{}) (int, error) {
	return fmt.Fprintf(stdout, f, args...)
}

func println(args ...interface{}) (int, error) {
	return fmt.Fprintln(stdout, args...)
}

func minInt(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func minUint(a, b uint) uint {
	if a < b {
		return a
	}
	return b
}

func minInt64(a, b int64) int64 {
	if a < b {
		return a
	}
	return b
}

func minUint64(a, b uint64) uint64 {
	if a < b {
		return a
	}
	return b
}

func maxInt(a, b int) int {
	if a < b {
		return b
	}
	return a
}

func maxUint(a, b uint) uint {
	if a < b {
		return b
	}
	return a
}
func maxInt64(a, b int64) int64 {
	if a < b {
		return b
	}
	return a
}

func maxUint64(a, b uint64) uint64 {
	if a < b {
		return b
	}
	return a
}

func absInt(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

func absInt64(a int64) int64 {
	if a < 0 {
		return -a
	}
	return a
}

// readString() string
// readInt() int
// readIntSlice(n int) []int
// readLengthAndSlice() []int
type town struct {
	id   int
	x, y int
}
type townSliceX []town

func (ts townSliceX) Len() int {
	return len(ts)
}
func (ts townSliceX) Less(i, j int) bool {
	return ts[i].x < ts[j].x
}
func (ts townSliceX) Swap(i, j int) {
	ts[i], ts[j] = ts[j], ts[i]
}

type townSliceY []town

func (ts townSliceY) Len() int {
	return len(ts)
}
func (ts townSliceY) Less(i, j int) bool {
	return ts[i].y < ts[j].y
}
func (ts townSliceY) Swap(i, j int) {
	ts[i], ts[j] = ts[j], ts[i]
}

type cost struct {
	val      int
	from, to int
}

type costSlice []cost

func (cs costSlice) Len() int {
	return len(cs)
}
func (cs costSlice) Less(i, j int) bool {
	return cs[i].val < cs[j].val
}
func (cs costSlice) Swap(i, j int) {
	cs[i], cs[j] = cs[j], cs[i]
}
func (cs *costSlice) Push(x interface{}) {
	item := x.(cost)
	*cs = append(*cs, item)
}
func (cs *costSlice) Pop() interface{} {
	c := *cs
	n := len(c) - 1
	if n == -1 {
		return nil
	}
	x := c[n]
	*cs = c[:n]
	return x
}

func main() {
	defer stdout.Flush()

	n := readInt()
	ts := make([]town, n)
	for i := 0; i < n; i++ {
		ts[i].id = i
		ts[i].x = readInt()
		ts[i].y = readInt()
	}

	E := make([][]cost, n)

	sort.Sort(townSliceX(ts))
	for i := 0; i+1 < n; i++ {
		a := ts[i].id
		b := ts[i+1].id
		c := absInt(ts[i].x - ts[i+1].x)
		E[a] = append(E[a], cost{c, a, b})
		E[b] = append(E[b], cost{c, b, a})
	}

	sort.Sort(townSliceY(ts))
	for i := 0; i+1 < n; i++ {
		a := ts[i].id
		b := ts[i+1].id
		c := absInt(ts[i].y - ts[i+1].y)
		E[a] = append(E[a], cost{c, a, b})
		E[b] = append(E[b], cost{c, b, a})
	}

	v := make(map[int]bool)

	h := new(costSlice)
	heap.Init(h)
	pop := func() (cost, bool) {
		x := heap.Pop(h)
		if x == nil {
			return cost{}, false
		}
		return x.(cost), true
	}

	push := func(c cost) {
		heap.Push(h, c)
	}

	v[0] = true
	for _, c := range E[0] {
		push(c)
	}

	var ans int64
	for len(v) != n {
		e, ok := pop()
		if !ok {
			panic("no edges found")
		}
		if v[e.to] {
			continue
		}
		ans += int64(e.val)
		v[e.to] = true
		for _, c := range E[e.to] {
			push(c)
		}
	}
	println(ans)
}


Measured memory_bytes: 48768