package main

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"os"
	"strconv"
)

var DEBUG = true

func main() {
	defer Flush()
	H := readi()
	W := readi()
	K := readi()

	x1 := readi() - 1
	y1 := readi() - 1
	x2 := readi() - 1
	y2 := readi() - 1

	c := make([][]byte, H)
	for i := range c {
		c[i] = readb()
	}

	pq := NewPriorityQueue(func(p, q PriorityQueueElement) bool {
		return p.d < q.d
	})
	push := func(x, y, d int) {
		pq.Push(PriorityQueueElement{x, y, d})
	}
	pop := func() (int, int, int) {
		res := pq.Pop()
		return res.x, res.y, res.d
	}

	d := make([][]int, H)
	for i := range d {
		d[i] = make([]int, W)
		for j := range d[i] {
			d[i][j] = INF
		}
	}

	d[x2][y2] = 0
	push(x2, y2, 0)

	dx := []int{-1, 0, 1, 0}
	dy := []int{0, -1, 0, 1}
	for pq.Len() != 0 {
		x, y, _ := pop()
		for dir := range dx {
			nd := d[x][y] + 1
			for k, nx, ny := 1, x+dx[dir], y+dy[dir]; k <= K && 0 <= nx && nx < H && 0 <= ny && ny < W && c[nx][ny] == '.'; k, nx, ny = k+1, nx+dx[dir], ny+dy[dir] {
				if d[nx][ny] < nd {
					break
				}
				if d[nx][ny] == nd {
					continue
				}
				//dbg("checking", nx, ny)
				d[nx][ny] = nd
				push(nx, ny, nd)
			}
		}
	}

	if d[x1][y1] == INF {
		println(-1)
	} else {
		println(d[x1][y1])
	}

	//for i := range d {
	//	dbg("d", d[i])
	//}
}

type PriorityQueueElement struct {
	x, y, d int
}

type PriorityQueue struct {
	a   []PriorityQueueElement
	cmp func(i, j int) bool
}

func NewPriorityQueue(cmp func(x, y PriorityQueueElement) bool) *PriorityQueue {
	pq := &PriorityQueue{
		a: make([]PriorityQueueElement, 0),
	}
	pq.cmp = func(i, j int) bool {
		return cmp(pq.a[i], pq.a[j])
	}
	return pq
}

func (pq *PriorityQueue) Len() int {
	return len(pq.a)
}

func (pq *PriorityQueue) parent(i int) int {
	return (i - 1) / 2
}

func (pq *PriorityQueue) lch(i int) int {
	return i*2 + 1
}

func (pq *PriorityQueue) rch(i int) int {
	return i*2 + 2
}

func (pq *PriorityQueue) swap(i, j int) {
	pq.a[i], pq.a[j] = pq.a[j], pq.a[i]
}

func (pq *PriorityQueue) Push(v PriorityQueueElement) {
	pq.a = append(pq.a, v)
	n := len(pq.a) - 1
	for i, p := n, pq.parent(n); 0 != i && !pq.cmp(p, i); i, p = p, pq.parent(p) {
		pq.swap(i, p)
	}
}

func (pq *PriorityQueue) Top() PriorityQueueElement {
	return pq.a[0]
}

func (pq *PriorityQueue) Pop() PriorityQueueElement {
	n := len(pq.a) - 1
	pq.a[0], pq.a[n] = pq.a[n], pq.a[0]
	res := pq.a[n]
	pq.a = pq.a[:n]
	p := 0
	for {
		l := pq.lch(p)
		r := pq.rch(p)

		if n <= l {
			// no children
			break
		}

		if n <= r {
			// p has l only
			if pq.cmp(p, l) {
				break
			}
			pq.swap(p, l)
			p = l
			continue
		}

		// p has l and r
		if pq.cmp(p, l) && pq.cmp(p, r) {
			break
		}

		if pq.cmp(p, l) {
			pq.swap(p, r)
			p = r
			continue
		}

		if pq.cmp(p, r) {
			pq.swap(p, l)
			p = l
			continue
		}

		// both l and r are prior to p
		if pq.cmp(l, r) {
			pq.swap(p, l)
			p = l
			continue
		}
		pq.swap(p, r)
		p = r
	}

	return res
}

// -----------------------------------------------------------------------------

// IO helper functions

// Returns next token from input.  It must be initialized by SetInput()
// before the first call.
var nextToken func() ([]byte, error)
var nextLine func() ([]byte, error)

// Holds a buffer for output.  It must be initialized by SetOutput().
// All IO fucntions (read*() and [e]print*()) should write to OutputWriter
// instead of this.
var OutputBuffer *bufio.Writer

// Holds an io.Writer.  It must be initialized by SetOutput()
var OutputWriter io.Writer

// Set IO functions for interactive input/output.
func SetInteractive(w io.Writer, r io.Reader) {
	SetUnbefferedInput(r)
	OutputBuffer = nil
	OutputWriter = w
}

// Setup OutputBuffer and OutputWriter.
func SetOutput(w io.Writer) {
	OutputBuffer = bufio.NewWriter(w)
	OutputWriter = OutputBuffer
}

// Flushes OutputBuffer
func Flush() {
	if OutputBuffer != nil {
		OutputBuffer.Flush()
	}
}

// Returns true if c is a white space
func IsSpace(c byte) bool {
	switch c {
	case '\t', '\n', '\v', '\f', '\r', ' ':
		return true
	}
	return false
}

func IsNewLine(c byte) bool {
	switch c {
	case '\n', '\r':
		return true
	}
	return false
}

// Setup nextToken with input buffer.
func SetInput(r io.Reader) {
	buf := new(bytes.Buffer)
	var b []byte

	var i int
	rest := func() ([]byte, error) {
		for i < len(b) && IsSpace(b[i]) {
			i++
		}
		if i == len(b) {
			return nil, io.ErrUnexpectedEOF
		}
		j := i
		for i < len(b) && !IsSpace(b[i]) {
			i++
		}
		return b[j:i], nil
	}
	initial := func() ([]byte, error) {
		io.Copy(buf, r)
		b = buf.Bytes()
		nextToken = rest
		return rest()
	}
	nextToken = initial

	restLn := func() ([]byte, error) {
		for i < len(b) && IsNewLine(b[i]) {
			i++
		}
		if i == len(b) {
			return nil, io.ErrUnexpectedEOF
		}
		j := i
		for i < len(b) && !IsNewLine(b[i]) {
			i++
		}
		return b[j:i], nil
	}

	initialLn := func() ([]byte, error) {
		io.Copy(buf, r)
		b = buf.Bytes()
		nextLine = restLn
		return restLn()
	}
	nextLine = initialLn
}

// Setup nextToken without input buffer.
func SetUnbefferedInput(r io.Reader) {
	buf := bufio.NewReader(r)
	var b []byte

	var i int
	nextToken = func() ([]byte, error) {
		var err error
		if i == len(b) {
			b, err = buf.ReadBytes('\n')
			if err != nil {
				return nil, err
			}
			i = 0
			j := len(b) - 1
			for 0 <= j && IsSpace(b[j]) {
				j--
			}
			b = b[0 : j+1]
		}
		for i < len(b) && IsSpace(b[i]) {
			i++
		}
		j := i
		for i < len(b) && !IsSpace(b[i]) {
			i++
		}
		if i == j {
			return nil, io.ErrUnexpectedEOF
		}
		return b[j:i], nil
	}
}

// -----------------------------------------------------------------------------

// IO functions

// Reads next token and return it as []byte
func readb() []byte {
	b, err := nextToken()
	if err != nil {
		panic(err)
	}
	return b[:len(b):len(b)]
}

// Reads next token and return it as string
func reads() string {
	return string(readb())
}

// Read next line as []byte.  Trailing '\n' will not be included.
// See also comments on readb()
func readbln() []byte {
	b, err := nextLine()
	if err != nil {
		panic(err)
	}
	return b[:len(b):len(b)]
}

// Read next line as string
func readsln() string {
	return string(readbln())
}

// Reads next token and return it as int64
func readll() int64 {
	i, err := strconv.ParseInt(reads(), 10, 64)
	if err != nil {
		panic(err.Error())
	}
	return i
}

// Reads next token and return it as int
func readi() int {
	return int(readll())
}

// Reads next token and return it as float64
func readf() float64 {
	f, err := strconv.ParseFloat(reads(), 64)
	if err != nil {
		panic(err.Error())
	}
	return f
}

// Write args to OutputWriter with the format f
func printf(f string, args ...interface{}) (int, error) {
	return fmt.Fprintf(OutputWriter, f, args...)
}

// Write args to OutputWriter without format
func println(args ...interface{}) (int, error) {
	return fmt.Fprintln(OutputWriter, args...)
}

// Write args to stderr with the format f
func eprintf(f string, args ...interface{}) (int, error) {
	return fmt.Fprintf(os.Stderr, f, args...)
}

// Write args to stderr without format
func eprintln(args ...interface{}) (int, error) {
	return fmt.Fprintln(os.Stderr, args...)
}

func dbgf(f string, args ...interface{}) {
	if !DEBUG {
		return
	}
	fmt.Fprintf(os.Stderr, f, args...)
}

func dbg(args ...interface{}) {
	if !DEBUG {
		return
	}
	fmt.Fprintln(os.Stderr, args...)
}

// -----------------------------------------------------------------------------

// Utilities

func sumSlice(a []int) int {
	var res int
	for _, v := range a {
		res += v
	}
	return res
}

func sumSlicell(a []int64) int64 {
	var res int64
	for _, v := range a {
		res += v
	}
	return res
}

func readInts(N int) (int, []int) {
	if N == 0 {
		N = readi()
	}
	a := make([]int, N)
	for i := range a {
		a[i] = readi()
	}
	return N, a
}

func readIntsll(N int) (int, []int64) {
	if N == 0 {
		N = readi()
	}
	a := make([]int64, N)
	for i := range a {
		a[i] = readll()
	}
	return N, a
}

// -----------------------------------------------------------------------------

// Simple math functions

const (
	// big prime
	INF  = 1000000007
	INF2 = 1000000009
	INF3 = 998244353
)

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func minll(a, b int64) int64 {
	if a < b {
		return a
	}
	return b
}

func minf(a, b float64) float64 {
	if a < b {
		return a
	}
	return b
}

func max(a, b int) int {
	if a < b {
		return b
	}
	return a
}

func maxll(a, b int64) int64 {
	if a < b {
		return b
	}
	return a
}

func maxf(a, b float64) float64 {
	if a < b {
		return b
	}
	return a
}

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

func absll(a int64) int64 {
	if a < 0 {
		return -a
	}
	return a
}

func absf(a float64) float64 {
	if a < 0 {
		return -a
	}
	return a
}

// egcd(a, b) returns d, x, y:
//   d is gcd(a,b)
//   x, y are  integers that satisfy ax + by = d
func egcd(a, b int) (int, int, int) {
	if b == 0 {
		return a, 1, 0
	}
	d, x, y := egcd(b, a%b)
	return d, y, x - a/b*y
}

func egcdll(a, b int64) (int64, int64, int64) {
	if b == 0 {
		return a, 1, 0
	}
	d, x, y := egcdll(b, a%b)
	return d, y, x - a/b*y
}

func gcd(a, b int) int {
	d, _, _ := egcd(a, b)
	return d
}

func gcdll(a, b int64) int64 {
	d, _, _ := egcdll(a, b)
	return d
}

// set up IO functions
func init() {
	// for non-interactive
	SetInput(os.Stdin)
	SetOutput(os.Stdout)

	// Enable below when interactive.  Its ok to leave above intact.
	// SetInteractive(os.Stdout, os.Stdin)
}


Measured memory_bytes: 21680