import java.io.BufferedReader
import java.io.InputStream
import java.io.InputStreamReader
import java.util.*
import kotlin.math.abs
import kotlin.math.max
import kotlin.math.min

val MOD = 1_000_000_007L

data class Entry(val h: Int, val w: Int, val cost: Int, val d: Int, val k: Int)
class Solver(stream: InputStream, private val out: java.io.PrintWriter) {
  fun solve() {
    val H = ni()
    val W = ni()
    val K = ni()
    val H1 = ni() - 1
    val W1 = ni() - 1
    val H2 = ni() - 1
    val W2 = ni() - 1
    val g = Array(H){ns().map{it == '.'}.toBooleanArray()}
    val INF = 1e9.toInt()
    val visited = Array(4){Array(H){BooleanArray(W)} }
    val dist = Array(4){Array(H){IntArray(W){INF} } }
    for (i in 0 until 4) {
      dist[i][H1][W1] = 0
    }

    val que = ArrayDeque<Entry>()
    que.add(Entry(H1, W1, 0, 0, K))

    val D = arrayOf(
      intArrayOf(1, 0),
      intArrayOf(-1, 0),
      intArrayOf(0, 1),
      intArrayOf(0, -1)
    )

    while(true) {
      val e = que.pollFirst() ?: break
      if (visited[e.d][e.h][e.w]) continue
      visited[e.d][e.h][e.w] = true

      for (d in 0 until 4) {
        val nh = e.h + D[d][0]
        val nw = e.w + D[d][1]
        if (nh in 0 until H && nw in 0 until W && g[nh][nw]) {
          val dcost = if (e.d == d && e.k < K) 0 else 1
          val ncost = e.cost + dcost
          if (ncost < dist[d][nh][nw]) {
            dist[d][nh][nw] = ncost
            val nk = if (e.d == d && e.k < K) e.k + 1 else 1
            if (dcost == 0) {
              que.addFirst(Entry(nh, nw, ncost, d, nk))
            } else {
              que.addLast(Entry(nh, nw, ncost, d, nk))
            }
          }
        }
      }
    }
    val ans = dist.map{it[H2][W2]}.min()
    if (ans == INF) out.println(-1)
    else out.println(ans)
  }













































  private val isDebug = try {
    // なんか本番でエラーでる
    System.getenv("MY_DEBUG") != null
  } catch (t: Throwable) {
    false
  }

  private var tokenizer: StringTokenizer? = null
  private val reader = BufferedReader(InputStreamReader(stream), 32768)
  private fun next(): String {
    while (tokenizer == null || !tokenizer!!.hasMoreTokens()) {
      tokenizer = StringTokenizer(reader.readLine())
    }
    return tokenizer!!.nextToken()
  }

  private fun ni() = next().toInt()
  private fun nl() = next().toLong()
  private fun ns() = next()
  private fun na(n: Int, offset: Int = 0): IntArray {
    return map(n) { ni() + offset }
  }
  private fun nal(n: Int, offset: Int = 0): LongArray {
    val res = LongArray(n)
    for (i in 0 until n) {
      res[i] = nl() + offset
    }
    return res
  }

  private fun na2(n: Int, offset: Int = 0): Array<IntArray> {
    val a  = Array(2){IntArray(n)}
    for (i in 0 until n) {
      for (e in a) {
        e[i] = ni() + offset
      }
    }
    return a
  }

  private inline fun map(n: Int, f: (Int) -> Int): IntArray {
    val res = IntArray(n)
    for (i in 0 until n) {
      res[i] = f(i)
    }
    return res
  }

  private inline fun debug(msg: () -> String) {
    if (isDebug) System.err.println(msg())
  }

  private fun debug(a: LongArray) {
    debug { a.joinToString(" ") }
  }

  private fun debug(a: IntArray) {
    debug { a.joinToString(" ") }
  }

  private fun debug(a: BooleanArray) {
    debug { a.map { if (it) 1 else 0 }.joinToString("") }
  }

  private fun debugDim(A: Array<LongArray>) {
    if (isDebug) {
      for (a in A) {
        debug(a)
      }
    }
  }
  private fun debugDim(A: Array<IntArray>) {
    if (isDebug) {
      for (a in A) {
        debug(a)
      }
    }
  }

  /**
   * 勝手にimport消されるのを防ぎたい
   */
  private fun hoge() {
    min(1, 2)
    max(1, 2)
    abs(-10)
  }
}

fun main() {
  val out = java.io.PrintWriter(System.out)
  Solver(System.`in`, out).solve()
  out.flush()
}

Measured memory_bytes: 85332