import java.io.*
import java.util.*
import java.lang.*
import java.lang.Math.*


class GridBfs(val G: Array<String>, val Wall:Char = '#',
              val Aisle:Char = '.') {
    val H = G.size
    val W = G[0].length
    init { }
    private val dx = intArrayOf(0,1,0,-1)
    private val dy = intArrayOf(1,0,-1,0)

    fun distance(SX: Int, SY: Int, GX: Int, GY: Int): Int {
        val dq = ArrayDeque<IntPair>()
        dq.add(IntPair(SX, SY))
        val dist = Array(H){IntArray(W){INF}}
        dist[SX][SY] = 0
        while (dq.isNotEmpty()) {
            val (x, y) = dq.removeFirst()!!
            if (x == GX && y == GY)  break

            for(i in dx.indices) {
                val nx = x + dx[i]; val ny = y + dy[i]
                if (nx<0 || H<=nx || ny<0 || W<=ny) {
                    continue
                }
                if (G[nx][ny] == Wall) {
                    continue
                }
                if (dist[nx][ny] > dist[x][y]) {
                    dist[nx][ny] = dist[x][y]
                    dq.addFirst(IntPair(nx, ny))
                }
            }

            for (i in x-2 .. x+2) {
                for (j in y-2 .. y+2) {
                    if (i<0 || H<=i || j<0 || W<=j) {
                        continue
                    }
                    if (G[i][j] == Wall) {
                        continue
                    }

                    if (dist[i][j] > dist[x][y]+1) {
                        dist[i][j] = dist[x][y]+1
                        dq.addLast(IntPair(i, j))
                    }
                }
            }
        }
        if (dist[GX][GY] != INF) {
            return dist[GX][GY]
        } else {
            return -1
        }
    }
}

fun solve() {
    val (H,W) = rd.readIntArray()
    val (SX, SY) = rd.readIntArray().map{it-1}
    val (GX, GY) = rd.readIntArray().map{it-1}
    val G = Array(H){""}
    for (i in 0 until H) {
        G[i] = rd.readString()
    }

    val gb = GridBfs(G)

    val ans = gb.distance(SX, SY, GX, GY)

    println(ans)
}


//val rd = debug.Reader("abc", "176", "d", "sample-1")
val rd = Reader()


fun main(args: Array<String>) {
    try {
        var exception: Throwable? = null
        val sth = Thread(null, SolveThread(), "solveThread", 128 * 1024 * 1024)
        sth.setUncaughtExceptionHandler { _, e -> exception = e }
        sth.start(); sth.join()
        if (exception != null) throw exception!! }
    catch (e: Exception) { throw e }
    finally { rd.close() }
}
const val MOD = 1_000_000_007L; const val INF = Int.MAX_VALUE/2; const val LINF = Long.MAX_VALUE/2
val EPS = 1e-9; fun DBLEQ(a: Double, b: Double): Boolean {return abs(a - b) < EPS}
data class IntPair(val first: Int, val second: Int); data class LongPair(val first: Long, val second: Long)
data class To(val idx: Int, val cost: Long)
fun <T>edge(V: Int): Array<ArrayList<T>> { return Array(V){ArrayList<T>()} }
val errPrintln: (Any) -> Unit = { msg -> System.err.println(msg) }
fun rAssert(exp: Boolean, lazyMsg: () -> String = {""}) {
    if (!exp) { val msg = lazyMsg(); errPrintln("EAssert Error: $msg"); throw Error(msg) }
}
fun tAssert(exp: Boolean, lazyMsg: () -> String = {""}) {
    if (!exp) { val msg = lazyMsg(); errPrintln("TAssert Error: $msg"); Thread.sleep(3000) }
}
class SolveThread : Runnable {
    override fun run() { solve() }
}
class Reader {
    private val br = BufferedReader(InputStreamReader(System.`in`))
    val readString: () -> String = { br.readLine() }
    val readInt: () -> Int = { br.readLine().toInt() }
    val readLong: () -> Long = { br.readLine().toLong() }
    val readIntArray: () -> IntArray = { br.readLine().split(' ').map { it.toInt() }.toIntArray() }
    val readLongArray: () -> LongArray = { br.readLine().split(' ').map { it.toLong() }.toLongArray() }
    val readListInt: () -> List<Int> = { br.readLine().split(' ').map { it.toInt() } }
    val readListLong: () -> List<Long> = { br.readLine().split(' ').map { it.toLong() } }
    val readListIntCol: (Int) -> List<Int> = { N -> (0 until N).map { readInt() } }
    val readListLongCol: (Int) -> List<Long> = { N -> (0 until N).map { readLong() } }
    val close: () -> Unit = { br.close() }
    protected fun finalize() { close() }
}


Measured memory_bytes: 61660