// solution is at the bottom

import kotlin.math.*

@JvmField val INPUT = System.`in`
@JvmField val OUTPUT = System.out

const val _BUFFER_SIZE = 1 shl 16
@JvmField val _buffer = ByteArray(_BUFFER_SIZE)
@JvmField var _bufferPt = 0
@JvmField var _bytesRead = 0

tailrec fun readChar(): Char {
    if(_bufferPt == _bytesRead) {
        _bufferPt = 0
        _bytesRead = INPUT.read(_buffer, 0, _BUFFER_SIZE)
    }
    return if(_bytesRead < 0) Char.MIN_VALUE
    else {
        val c = _buffer[_bufferPt++].toChar()
        if (c == '\r') readChar()
        else c
    }
}

fun readLine(): String? {
    var c = readChar()
    return if(c == Char.MIN_VALUE) null
    else buildString {
        while(true) {
            when(c) {
                '\n', Char.MIN_VALUE -> return@buildString
                else -> {
                    append(c)
                    c = readChar()
                }
            }
        }
    }
}
fun readLn() = readLine()!!

fun read() = buildString {
    var c = readChar()
    while(c <= ' ') {
        if(c == Char.MIN_VALUE) return@buildString
        c = readChar()
    }
    do {
        append(c)
        c = readChar()
    } while(c > ' ')
}
fun readInt() = read().toInt()
fun readDouble() = read().toDouble()
fun readLong() = read().toLong()
fun readStrings(n: Int) = List(n) { read() }
fun readLines(n: Int) = List(n) { readLn() }
fun readInts(n: Int) = List(n) { read().toInt() }
fun readIntArray(n: Int) = IntArray(n) { read().toInt() }
fun readDoubles(n: Int) = List(n) { read().toDouble() }
fun readDoubleArray(n: Int) = DoubleArray(n) { read().toDouble() }
fun readLongs(n: Int) = List(n) { read().toLong() }
fun readLongArray(n: Int) = LongArray(n) { read().toLong() }


fun main() {
    val (n, m) = readIntArray(2)
    val (fromi, fromj) = readIntArray(2)
    val (toi, toj) = readIntArray(2)
    val aa = Array(n) {""}
    for (i in 0 until n) {
        aa[i] = read()
    }

    val a = Array(n) {IntArray(m) {-1} }
    for (i in 0 until n) {
        for (j in 0 until m) {
            if (aa[i][j] == '#') {
                a[i][j] = -2
            }
        }
    }

    val group = Array(n) {IntArray(m) {-1} }
    var groupCount = 0

    val dd = listOf(Pair(-1, 0), Pair(1, 0), Pair(0, -1), Pair(0, 1))

    for (i in 0 until n) {
        for (j in 0 until m) {
            if (a[i][j] == -1 && group[i][j] == -1) {
                group[i][j] = groupCount
                val queue = mutableListOf<Pair<Int, Int>>()
                queue.add(Pair(i, j))
                var queueIdx = 0

                while (queueIdx < queue.size) {
                    val (y, x) = queue[queueIdx++]
                    for ((dy, dx) in dd) {
                        val toy = y + dy
                        val tox = x + dx

                        if (tox >= 0 && toy >= 0 && toy < n && tox < m && a[toy][tox] == -1 && group[toy][tox] == -1) {
                            group[toy][tox] = groupCount
                            queue.add(Pair(toy, tox))
                        }
                    }
                }

                groupCount++
            }
        }
    }


    val graph = Array(groupCount) { mutableSetOf<Int>()}

    for (i in 0 until n) {
        for (j in 0 until m) {
            if (a[i][j] != -2) {
                val fromGroup = group[i][j]

                for (dx in -2..2) {
                    for (dy in -2..2) {
                        val toi = i + dx
                        val toj = j + dy

                        if (toi >= 0 && toj >= 0 && toi < n && toj < m) {

                            val toGroup = group[toi][toj]
                            if (toGroup != -1 && fromGroup != toGroup) {
                                graph[fromGroup].add(toGroup)
                                graph[toGroup].add(fromGroup)
                            }
                        }
                    }
                }
            }
        }
    }

    val startGroup = group[fromi - 1][fromj - 1]
    val endGroup = group[toi - 1][toj - 1]
    val dist = IntArray(groupCount) {-1}
    dist[startGroup] = 0

    val queue = mutableListOf<Int>(startGroup)
    var queueIdx = 0

    while (queueIdx < queue.size) {
        val cur = queue[queueIdx++]

        for (to in graph[cur]) {
            if (dist[to] == -1) {
                dist[to] = dist[cur] + 1
                queue.add(to)
            }
        }
    }

    println(dist[endGroup])

    //println(group.map { it.joinToString(" ") }.joinToString("\n"))
}


Measured memory_bytes: 109064