import kotlin.math.min

fun main() = abc176d()

@OptIn(ExperimentalStdlibApi::class)
fun abc176d() = IO_abc176d().exec {
    val (h, w) = readInt() to readInt()
    val (startY, startX) = readInt() - 1 to readInt() - 1
    val (goalY, goalX) = readInt() - 1 to readInt() - 1
    val grid = Array(h) { readString().map { it == '.' }.toBooleanArray() }

    data class Q(val y: Int, val x: Int, val warpCount: Long) {
        override fun equals(other: Any?): Boolean {
            if (this === other) return true
            if (other !is Q) return false

            if (y != other.y) return false
            if (x != other.x) return false

            return true
        }

        override fun hashCode(): Int {
            var result = y
            result = 31 * result + x
            return result
        }
    }

    val inf = Long.MAX_VALUE / 100
    val queue = ArrayDeque<Q>()
    val around = listOf(-1 to 0, 1 to 0, 0 to -1, 0 to 1)
    val mins = Array(h) { LongArray(w) { inf } }

    queue.add(Q(startY, startX, 0))

    while (queue.isNotEmpty()) {
        val (y, x, warpCount) = queue.removeFirst()

        if (mins[y][x] <= warpCount) continue
        mins[y][x] = min(mins[y][x], warpCount)

        around.map { (addY, addX) -> Q(y + addY, x + addX, warpCount) }.filter {
            it.y in 0 until h && it.x in 0 until w &&
                    grid[it.y][it.x] &&
                    warpCount < mins[it.y][it.x]
        }.forEach { queue.addFirst(it) }

        for (addY in -2..2) for (addX in -2..2) {
            if (addY == 0 && addX == 0) continue
            val q = Q(y + addY, x + addX, warpCount + 1)
            if (q.y in 0 until h && q.x in 0 until w &&
                grid[q.y][q.x] &&
                warpCount < mins[q.y][q.x]
            ) {
                queue.addLast(q)
            }
        }
    }

    val answer = mins[goalY][goalX].takeIf { it != inf } ?: -1

    println(answer)
}

// region kokokara template dayo (^o^)
@Suppress("unused", "ClassName", "SpellCheckingInspection", "ConvertToStringTemplate", "MemberVisibilityCanBePrivate")
private class IO_abc176d(private val separator: String = System.lineSeparator()) {
    private val input = System.`in`
    private val buffer = ByteArray(1024)
    private var pointer = 0
    private var bufferLength = 0
    private val sb = StringBuilder()
    private fun Byte.isPrintable() = this in 33..126
    private fun Byte.isNumeric() = this in '0'.toByte()..'9'.toByte()
    private fun Byte.toNumVal() = if (this.isNumeric()) this - '0'.toByte() else error("$this is not numeric")

    private fun hasNextByte(): Boolean {
        return if (pointer < bufferLength) true else {
            pointer = 0
            bufferLength = input.read(buffer)
            bufferLength > 0
        }
    }

    private fun readByte(): Byte = if (hasNextByte()) buffer[pointer++] else -1
    private fun skipUnprintable() = run { while (hasNextByte() && !buffer[pointer].isPrintable()) pointer++ }
    private fun hasNext(): Boolean = run { skipUnprintable() }.run { hasNextByte() }
    private fun hasNextOrError() = if (!hasNext()) error("has no next element.") else Unit

    fun readString(): String {
        hasNextOrError()
        val sb = StringBuilder()
        var b = readByte()
        while (b.isPrintable()) {
            sb.appendCodePoint(b.toInt())
            b = readByte()
        }
        return sb.toString()
    }

    fun readLong(): Long {
        hasNextOrError()
        var n = 0L
        var negative = false
        var b = readByte()
        if (b == '-'.toByte()) {
            negative = true
            b = readByte()
        }
        if (!b.isNumeric()) error("$b is not numeric.")
        while (true) {
            when {
                b.isNumeric() -> n = n * 10 + b.toNumVal()
                b.toInt() == -1 || !b.isPrintable() -> return if (negative) -n else n
                else -> error("failed to parse. [n=$n, b=$b]")
            }
            b = readByte()
        }
    }

    fun readInt() = readLong()
        .let { if (it in Int.MIN_VALUE..Int.MAX_VALUE) it.toInt() else error("$it is not in range of Int.") }

    fun readDouble(): Double {
        var n = 0.0
        var div = 1.0
        var negative = false
        var b = readByte()
        if (b == '-'.toByte()) {
            negative = true
            b = readByte()
        }
        do n = n * 10 + b.toNumVal()
        while (run { b = readByte() }.run { b.isNumeric() })
        if (b == '.'.toByte()) {
            while (run { b = readByte() }.run { b.isNumeric() })
                n += b.toNumVal() / (run { div *= 10 }.run { div })
        }
        return if (negative) -n else n
    }

    fun println(): Unit = run { sb.append(separator) }
    fun print(any: Any): Unit = run { sb.append(any) }
    fun println(any: Any): Unit = run { sb.append(any.toString() + separator) }
    fun flush() = run { kotlin.io.println(sb); sb.clear() }

    fun exec(action: IO_abc176d.() -> Unit) {
        var t: Throwable? = null
        Thread(null, { action() }, "solve", 128 * 1024 * 1024)
            .apply { setUncaughtExceptionHandler { _, t1 -> t = t1 } }
            .apply { start() }.join()
        t?.let { throw it }
        kotlin.io.print(sb)
    }

    fun readLine(): Nothing = error("readLine is disabled.")
}
// endregion kokomade template dayo (^o^)


Measured memory_bytes: 79832