/*
URL:
https://atcoder.jp/contests/abc176/tasks/abc176_d
*/

package main

import (
	"bufio"
	"fmt"
	"io"
	"math"
	"os"
	"strconv"
)

var (
	h, w           int
	sy, sx, gy, gx int
	S              [][]rune

	G [][]Edge
)

func main() {
	h, w = ReadInt2()
	sy, sx = ReadInt2()
	gy, gx = ReadInt2()
	sy--
	sx--
	gy--
	gx--
	for i := 0; i < h; i++ {
		row := ReadRuneSlice()
		S = append(S, row)
	}

	steps := [4][2]int{{0, 1}, {0, -1}, {1, 0}, {-1, 0}}
	toid := func(i, j int) int { return w*i + j }
	// toy := func(id int) int { return id / w }
	// tox := func(id int) int { return id % w }
	worps := [][2]int{}
	for i := -2; i <= 2; i++ {
		for j := -2; j <= 2; j++ {
			if i == 0 && j == 0 {
				continue
			}

			need := true
			for _, st := range steps {
				if st[0] == i && st[1] == j {
					need = false
					break
				}
			}

			if need {
				worps = append(worps, [2]int{i, j})
			}

			// worps = append(worps, [2]int{i, j})
		}
	}

	N := h * w
	G = make([][]Edge, N)
	for i := 0; i < h; i++ {
		for j := 0; j < w; j++ {
			if S[i][j] == '#' {
				continue
			}

			cid := toid(i, j)

			for _, s := range steps {
				dy, dx := s[0], s[1]
				ny, nx := i+dy, j+dx
				if 0 <= ny && ny < h && 0 <= nx && nx < w && S[ny][nx] == '.' {
					nid := toid(ny, nx)

					G[cid] = append(G[cid], Edge{to: nid, cost: 0})
				}
			}

			for _, s := range worps {
				dy, dx := s[0], s[1]
				ny, nx := i+dy, j+dx
				if 0 <= ny && ny < h && 0 <= nx && nx < w && S[ny][nx] == '.' {
					nid := toid(ny, nx)

					G[cid] = append(G[cid], Edge{to: nid, cost: 1})
				}
			}
		}
	}

	sid := toid(sy, sx)
	gid := toid(gy, gx)
	// dp, _ := dijkstra(sid, N, G[:N])
	dp, visited := SSSPBy01BFS(sid, N, G[:N])
	// if dp[gid] >= INF_BIT30 {
	if !visited[gid] {
		fmt.Println(-1)
	} else {
		fmt.Println(dp[gid])
	}
}

type Edge struct {
	to, cost int
}

// verified by https://atcoder.jp/contests/abc176/tasks/abc176_d
func SSSPBy01BFS(sid, n int, AG [][]Edge) (dp []int, visited []bool) {
	dp = make([]int, n)
	visited = make([]bool, n)

	for i := 0; i < n; i++ {
		dp[i] = INF_BIT30
		visited[i] = false
	}

	dp[sid] = 0
	Q := NewDeque()
	Q.PushFront(sid)

	for Q.Len() > 0 {
		cid := Q.PopBack()
		visited[cid] = true

		for _, e := range G[cid] {
			if visited[e.to] {
				continue
			}

			if dp[e.to] > dp[cid]+e.cost {
				dp[e.to] = dp[cid] + e.cost
				if e.cost == 0 {
					Q.PushBack(e.to)
				} else {
					Q.PushFront(e.to)
				}
			}
		}
	}

	return dp, visited
}

type Deque struct {
	front, back []int
}

func NewDeque() *Deque {
	d := new(Deque)
	d.front, d.back = []int{}, []int{}
	return d
}

func (d *Deque) Len() int {
	return len(d.front) + len(d.back)
}

func (d *Deque) PushFront(a int) {
	d.front = append(d.front, a)
}

func (d *Deque) PushBack(a int) {
	d.back = append(d.back, a)
}

func (d *Deque) PopFront() int {
	if len(d.front) > 0 {
		pop := d.front[len(d.front)-1]
		d.front = d.front[:len(d.front)-1]
		return pop
	}

	if len(d.back) == 0 {
		panic("deque is empty")
	}

	pop := d.back[0]
	d.back = d.back[1:]
	return pop
}

func (d *Deque) PopBack() int {
	if len(d.back) > 0 {
		pop := d.back[len(d.back)-1]
		d.back = d.back[:len(d.back)-1]
		return pop
	}

	if len(d.front) == 0 {
		panic("deque is empty")
	}

	pop := d.front[0]
	d.front = d.front[1:]
	return pop
}

func (d *Deque) List() []int {
	res := []int{}
	for i := len(d.back) - 1; i >= 0; i-- {
		res = append(res, d.back[i])
	}
	for i := 0; i < len(d.front); i++ {
		res = append(res, d.front[i])
	}
	return res
}

/*******************************************************************/

/********** common constants **********/

const (
	// General purpose
	MOD = 1000000000 + 7
	// MOD          = 998244353
	ALPHABET_NUM = 26
	INF_INT64    = math.MaxInt64
	INF_BIT60    = 1 << 60
	INF_INT32    = math.MaxInt32
	INF_BIT30    = 1 << 30
	NIL          = -1

	// for dijkstra, prim, and so on
	WHITE = 0
	GRAY  = 1
	BLACK = 2
)

/********** bufio setting **********/

func init() {
	// bufio.ScanWords <---> bufio.ScanLines
	ReadString = newReadString(os.Stdin, bufio.ScanWords)
	stdout = bufio.NewWriter(os.Stdout)
}

/********** FAU standard libraries **********/

//fmt.Sprintf("%b\n", 255) 	// binary expression

/********** I/O usage **********/

//str := ReadString()
//i := ReadInt()
//X := ReadIntSlice(n)
//S := ReadRuneSlice()
//a := ReadFloat64()
//A := ReadFloat64Slice(n)

//str := ZeroPaddingRuneSlice(num, 32)
//str := PrintIntsLine(X...)

/*********** Input ***********/

var (
	// ReadString returns a WORD string.
	ReadString func() string
	stdout     *bufio.Writer
)

func newReadString(ior io.Reader, sf bufio.SplitFunc) func() string {
	r := bufio.NewScanner(ior)
	r.Buffer(make([]byte, 1024), int(1e+9)) // for Codeforces
	r.Split(sf)

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

// ReadInt returns an integer.
func ReadInt() int {
	return int(readInt64())
}
func ReadInt2() (int, int) {
	return int(readInt64()), int(readInt64())
}
func ReadInt3() (int, int, int) {
	return int(readInt64()), int(readInt64()), int(readInt64())
}
func ReadInt4() (int, int, int, int) {
	return int(readInt64()), int(readInt64()), int(readInt64()), int(readInt64())
}

// ReadInt64 returns as integer as int64.
func ReadInt64() int64 {
	return readInt64()
}
func ReadInt64_2() (int64, int64) {
	return readInt64(), readInt64()
}
func ReadInt64_3() (int64, int64, int64) {
	return readInt64(), readInt64(), readInt64()
}
func ReadInt64_4() (int64, int64, int64, int64) {
	return readInt64(), readInt64(), readInt64(), readInt64()
}

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

// ReadIntSlice returns an integer slice that has n integers.
func ReadIntSlice(n int) []int {
	b := make([]int, n)
	for i := 0; i < n; i++ {
		b[i] = ReadInt()
	}
	return b
}

// ReadInt64Slice returns as int64 slice that has n integers.
func ReadInt64Slice(n int) []int64 {
	b := make([]int64, n)
	for i := 0; i < n; i++ {
		b[i] = ReadInt64()
	}
	return b
}

// ReadFloat64 returns an float64.
func ReadFloat64() float64 {
	return float64(readFloat64())
}

func readFloat64() float64 {
	f, err := strconv.ParseFloat(ReadString(), 64)
	if err != nil {
		panic(err.Error())
	}
	return f
}

// ReadFloatSlice returns an float64 slice that has n float64.
func ReadFloat64Slice(n int) []float64 {
	b := make([]float64, n)
	for i := 0; i < n; i++ {
		b[i] = ReadFloat64()
	}
	return b
}

// ReadRuneSlice returns a rune slice.
func ReadRuneSlice() []rune {
	return []rune(ReadString())
}

/*********** Output ***********/

// PrintIntsLine returns integers string delimited by a space.
func PrintIntsLine(A ...int) string {
	res := []rune{}

	for i := 0; i < len(A); i++ {
		str := strconv.Itoa(A[i])
		res = append(res, []rune(str)...)

		if i != len(A)-1 {
			res = append(res, ' ')
		}
	}

	return string(res)
}

// PrintIntsLine returns integers string delimited by a space.
func PrintInts64Line(A ...int64) string {
	res := []rune{}

	for i := 0; i < len(A); i++ {
		str := strconv.FormatInt(A[i], 10) // 64bit int version
		res = append(res, []rune(str)...)

		if i != len(A)-1 {
			res = append(res, ' ')
		}
	}

	return string(res)
}

// PrintfBufStdout is function for output strings to buffered os.Stdout.
// You may have to call stdout.Flush() finally.
func PrintfBufStdout(format string, a ...interface{}) {
	fmt.Fprintf(stdout, format, a...)
}

/*********** Debugging ***********/

// PrintfDebug is wrapper of fmt.Fprintf(os.Stderr, format, a...)
func PrintfDebug(format string, a ...interface{}) {
	fmt.Fprintf(os.Stderr, format, a...)
}

// ZeroPaddingRuneSlice returns binary expressions of integer n with zero padding.
// For debugging use.
func ZeroPaddingRuneSlice(n, digitsNum int) []rune {
	sn := fmt.Sprintf("%b", n)

	residualLength := digitsNum - len(sn)
	if residualLength <= 0 {
		return []rune(sn)
	}

	zeros := make([]rune, residualLength)
	for i := 0; i < len(zeros); i++ {
		zeros[i] = '0'
	}

	res := []rune{}
	res = append(res, zeros...)
	res = append(res, []rune(sn)...)

	return res
}


Measured memory_bytes: 239536