@file:Suppress("NOTHING_TO_INLINE", "EXPERIMENTAL_FEATURE_WARNING", "OVERRIDE_BY_INLINE")

import java.io.PrintWriter
import java.util.EnumMap
import java.util.SortedMap
import java.util.TreeMap
import kotlin.math.*
import kotlin.random.Random
import kotlin.collections.sort as _sort
import kotlin.collections.sortDescending as _sortDescending
import kotlin.io.println as iprintln

/** @author Spheniscine */
fun main() { _writer.solve(); _writer.flush() }
fun PrintWriter.solve() {
    val numCases = 1//readInt()
    case@ for(case in 1..numCases) {
        //print("Case #$case: ")

        object {
            val n = readInt()
            val m = readInt()
            val k = readInt()

            val x1 = readInt()-1
            val y1 = readInt()-1
            val x2 = readInt()-1
            val y2 = readInt()-1

            val G = readLines(n)

            val R = Array(n) { CompressionSet2(m) }
            val C = Array(m) { CompressionSet2(n) }

            fun remove(i: Int, j: Int) {
                R[i].remove(j)
                C[j].remove(i)
            }

            val Q = IntDeque()

            fun visit(i: Int, j: Int): Boolean {
                if(G[i][j] == '@') return false
                remove(i, j)
                Q.add(i); Q.add(j)
                return true
            }

            init {
                visit(x1, y1)

                val ans = run ans@{
                    var cost = 0
                    while (Q.isNotEmpty()) {
                        repeat(Q.size / 2) {
                            val i = Q.remove()
                            val j = Q.remove()

                            if(i == x2 && j == y2) return@ans cost
                            run {
                                R[i].forEach(j, j + k + 1) { nj ->
                                    if(!visit(i, nj)) return@run
                                }
                            }

                            run {
                                R[i].forEachDesc(j, j-k-1) { nj ->
                                    if(!visit(i, nj)) return@run
                                }
                            }

                            run {
                                C[j].forEach(i, i+k+1) { ni ->
                                    if(!visit(ni, j)) return@run
                                }
                            }

                            run {
                                C[j].forEachDesc(i, i-k-1) { ni ->
                                    if(!visit(ni, j)) return@run
                                }
                            }
                        }
                        cost++
                    }

                    -1
                }

                println(ans)
            }
        }
    }
}

open class CompressionSet(val n: Int) {
    private val N = IntArray(n+1) { it }
    var size = n
        private set

    tailrec fun ceiling(v: Int): Int =
        if(N[v] == v) v else {
            N[v] = N[N[v]]
            ceiling(N[v])
        }

    open fun remove(v: Int): Boolean {
        if(N[v] != v) return false
        N[v] = ceiling(v+1)
        size--
        return true
    }

    operator fun contains(v: Int) = N[v] == v

    inline fun forEach(start: Int, endx: Int, act: (Int) -> Unit) {
        val endx = min(endx, n)
        var i = ceiling(start)
        while(i < endx) {
            act(i)
            i = ceiling(i+1)
        }
    }

    operator fun iterator() = object: IntIterator() {
        private var next = ceiling(0)

        override fun hasNext() = next < n

        override fun nextInt(): Int {
            if(!hasNext()) throw NoSuchElementException()
            return next.also { next = ceiling(next+1) }
        }
    }
}

class CompressionSet2(n: Int): CompressionSet(n) {
    private val back = CompressionSet(n)
    private inline fun revIdx(i: Int) = n-1-i

    override fun remove(v: Int): Boolean {
        back.remove(revIdx(v))
        return super.remove(v)
    }

    fun floor(v: Int) = revIdx(back.ceiling(revIdx(v)))

    inline fun forEachDesc(start: Int, endx: Int, act: (Int) -> Unit) {
        val endx = max(endx, -1)
        var i = floor(start)
        while(i > endx) {
            act(i)
            i = floor(i-1)
        }
    }
}

class IntDeque(capacity: Int = 12){
    private var arr = IntArray(capacity)
    var size = 0
        private set
    inline val lastIndex get() = size - 1
    inline val indices get() = 0 until size

    private inline val capacity get() = arr.size

    inline fun isEmpty() = size == 0
    inline fun isNotEmpty() = size != 0

    private var head = 0

    private fun grow(minCapacity: Int = 8) {
        val newCapacity = maxOf(minCapacity, capacity + (capacity shr 1))
        val new = IntArray(newCapacity)
        for(i in 0 until size) new[i] = get(i)
        arr = new
        head = 0
    }

    private fun incHead() {
        head++
        if(head == capacity) head = 0
    }

    private fun decHead() {
        if(head == 0) head = capacity - 1
        else head--
    }

    private fun index(i: Int) = (head + i).let { if(it >= capacity) it - capacity else it }

    fun add(index: Int, element: Int) {
        if(size == capacity) grow()
        if(index < size / 2) {
            decHead()
            size++
            for(i in 0 until index) {
                set(i, get(i+1))
            }
        } else {
            size++
            for(i in size - 2 downTo index) {
                set(i+1, get(i))
            }
        }
        set(index, element)
    }

    fun addLast(e: Int) {
        if(size == capacity) grow()
        arr[index(size)] = e
        size++
    }
    inline fun add(e: Int) = addLast(e)

    val first get() = get(0)
    val last get() = get(lastIndex)

    fun removeFirst(): Int {
        val e = get(0)
        incHead()
        size--
        return e
    }
    inline fun remove() = removeFirst()
    fun removeLast(): Int {
        val e = get(lastIndex)
        size--
        return e
    }

    fun addFirst(e: Int) {
        if(size == capacity) grow()
        decHead()
        arr[head] = e
        size++
    }

    operator fun get(index: Int): Int {
        require(index in 0 until size)
        return arr[index(index)]
    }

    fun removeAt(index: Int): Int {
        val e = get(index)
        if(index < size / 2) {
            for(i in index - 1 downTo 0) {
                set(i+1, get(i))
            }
            incHead()
        } else {
            for(i in index until size - 1) {
                set(i, get(i+1))
            }
        }
        size--
        return e
    }

    operator fun set(index: Int, element: Int): Int {
        val old = get(index)
        arr[index(index)] = element
        return old
    }

    operator fun iterator() = object: IntIterator() {
        var i = 0
        override fun hasNext(): Boolean = i < size
        override fun nextInt(): Int = get(i++)
    }
}

/** IO */
//@JvmField val INPUT = File("input.txt").inputStream()
//@JvmField val OUTPUT = File("output.txt").outputStream()
@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() }

@JvmField val _writer = PrintWriter(OUTPUT, false)

/** shuffles and sort overrides to avoid quicksort attacks */
private inline fun <T> _shuffle(rnd: Random, get: (Int) -> T, set: (Int, T) -> Unit, size: Int) {
    // Fisher-Yates shuffle algorithm
    for (i in size - 1 downTo 1) {
        val j = rnd.nextInt(i + 1)
        val temp = get(i)
        set(i, get(j))
        set(j, temp)
    }
}

@JvmField var _random: Random? = null
val random get() = _random ?: Random(0x594E215C123 * System.nanoTime()).also { _random = it }

fun IntArray.shuffle(rnd: Random = random) = _shuffle(rnd, ::get, ::set, size)
fun IntArray.sort() { shuffle(); _sort() }
fun IntArray.sortDescending() { shuffle(); _sortDescending() }

fun LongArray.shuffle(rnd: Random = random) = _shuffle(rnd, ::get, ::set, size)
fun LongArray.sort() { shuffle(); _sort() }
fun LongArray.sortDescending() { shuffle(); _sortDescending() }

fun DoubleArray.shuffle(rnd: Random = random) = _shuffle(rnd, ::get, ::set, size)
fun DoubleArray.sort() { shuffle(); _sort() }
fun DoubleArray.sortDescending() { shuffle(); _sortDescending() }

fun CharArray.shuffle(rnd: Random = random) = _shuffle(rnd, ::get, ::set, size)
inline fun CharArray.sort() { _sort() }
inline fun CharArray.sortDescending() { _sortDescending() }

inline fun <T: Comparable<T>> Array<out T>.sort() = _sort()
inline fun <T: Comparable<T>> Array<out T>.sortDescending() = _sortDescending()
inline fun <T: Comparable<T>> MutableList<out T>.sort() = _sort()
inline fun <T: Comparable<T>> MutableList<out T>.sortDescending() = _sortDescending()

fun `please stop removing these imports IntelliJ`() { iprintln(max(1, 2)) }

/** additional commons */
inline fun <T> Iterable<T>.sumByLong(func: (T) -> Long) = fold(0L) { acc, t -> acc + func(t) }
inline fun <T> Sequence<T>.sumByLong(func: (T) -> Long) = fold(0L) { acc, t -> acc + func(t) }
inline fun <T> Array<T>.sumByLong(func: (T) -> Long) = fold(0L) { acc, t -> acc + func(t) }
fun IntArray.sumLong() = fold(0L, Long::plus)

Measured memory_bytes: 171848