// https://atcoder.jp/contests/abc170/submissions/14358430
// with line 67 modified
using System;
using System.Text;
using System.Diagnostics;
using System.Numerics;
using System.Collections.Generic;
 
class Myon
 
{
    public Myon() { }
    public static int Main()
    {
        cin = new Scanner();
        new Myon().calc();
        return 0;
    }
    static Scanner cin;
 
 
    int H, W, K;
 
    void calc()
    {
        H = cin.nextInt();
        W = cin.nextInt();
        K = cin.nextInt();
        int fy, fx, gy, gx;
        fy = cin.nextInt() - 1;
        fx = cin.nextInt() - 1;
        gy = cin.nextInt() - 1;
        gx = cin.nextInt() - 1;
 
        string[] board = new string[H];
        for (int i = 0; i < H; i++)
        {
            board[i] = cin.next();
        }
 
        int MAX = (int)1e8;
 
        int[,] dist = new int[H, W];
        for (int i = 0; i < H; i++)
        {
            for (int j = 0; j < W; j++)
            {
                dist[i, j] = MAX;
            }
        }
        Queue<Tuple<int, int>> q = new Queue<Tuple<int, int>>();
        dist[fy, fx] = 0;
        q.Enqueue(Tuple.Create(fy, fx));
        int[] vy = { 1, 0, -1, 0 };
        int[] vx = { 0, 1, 0, -1 }; 
        while (q.Count > 0)
        {
            var now = q.Dequeue();
            int y = now.Item1;
            int x = now.Item2;
            for (int k = 0; k < vy.Length; k++)
            {
                for (int l = 1; l <= K; l++)
                {
                    int ny = y + vy[k] * l;
                    int nx = x + vx[k] * l;
                    if (!inside(ny, nx)) break;
                    if (board[ny][nx] == '@') break;
                    if (!(dist[ny, nx] == MAX || dist[ny, nx] == dist[y, x] + 1)) break;
                    if(dist[ny,nx] > dist[y,x] + 1)
                    {
                        dist[ny, nx] = dist[y, x] + 1;
                        q.Enqueue(Tuple.Create(ny, nx));
                    }
                }
            }
        }
        if (dist[gy, gx] == MAX) Console.WriteLine(-1);
        else Console.WriteLine(dist[gy, gx]);
    }
 
    bool inside(int y, int x)
    {
        return y >= 0 && x >= 0 && y < H && x < W;
    } 
 
}
 
 
class Scanner
{
    string[] s;
    int i;
 
    char[] cs = new char[] { ' ' };
 
    public Scanner()
    {
        s = new string[0];
        i = 0;
    }
 
    public string next()
    {
        if (i < s.Length) return s[i++];
        string st = Console.ReadLine();
        while (st == "") st = Console.ReadLine();
        s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
        if (s.Length == 0) return next();
        i = 0;
        return s[i++];
    }
 
    public int nextInt()
    {
        return int.Parse(next());
    }
    public int[] ArrayInt(int N, int add = 0)
    {
        int[] Array = new int[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextInt() + add;
        }
        return Array;
    }
 
    public long nextLong()
    {
        return long.Parse(next());
    }
 
    public long[] ArrayLong(int N, long add = 0)
    {
        long[] Array = new long[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextLong() + add;
        }
        return Array;
    }
 
    public double nextDouble()
    {
        return double.Parse(next());
    }
 
 
    public double[] ArrayDouble(int N, double add = 0)
    {
        double[] Array = new double[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextDouble() + add;
        }
        return Array;
    }
}

Measured memory_bytes: 49408