using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using static System.Console;
using static System.Math;
using static MyIO;
using static MyUtil;

public class F { public static void Main() => (new Solver()).Solve(); }

public class Solver
{
	private const long INF = (long)1e18;
	private long[] di = new long[] { -1, 0, 1, 0 };
	private long[] dj = new long[] { 0, -1, 0, 1 };

	private long H;
	private long W;
	private long K;
	private long si;
	private long sj;
	private long ti;
	private long tj;
	private char[,] grid;
	private long[] dist;
	private PriorityQueue<(long, long)> pq;

	public void Solve()
	{
		H = GetLong();
		W = GetLong();
		K = GetLong();
		si = GetLong() - 1;
		sj = GetLong() - 1;
		ti = GetLong() - 1;
		tj = GetLong() - 1;
		grid = new char[H, W];
		for(long i = 0; i < H; i++)
		{
			var c = GetString().ToCharArray();
			for(long j = 0; j < W; j++)
				grid[i, j] = c[j];
		}

		dist = Enumerable.Repeat(INF, (int)(H * W * 4)).ToArray();
		pq = new PriorityQueue<(long, long)>(H * W * 4, (x, y) => x.CompareTo(y));

		for(long v = 0; v < 4; v++)
			push(si, sj, v, 0);

		while(pq.Count > 0)
		{
			var (d, id) = pq.Pop();
			if(dist[id] != d)
				continue;

			long i = id / W / 4;
			long j = (id / 4) % W;
			long v = id % 4;
			for(long nv = 0; nv < 4; nv++)
				push(i, j, nv, modCeil(d));

			long ni = i + di[v];
			long nj = j + dj[v];
			if(0 <= ni && ni < H && 0 <= nj && nj < W)
			{
				if(grid[ni, nj] == '.')
					push(ni, nj, v, d + 1);
			}
		}

		long ans = INF;
		for(long v = 0; v < 4; v++)
			chmin(ref ans, dist[toId(ti, tj, v)]);

		if(ans == INF)
			WriteLine(-1);
		else
		{
			ans = modCeil(ans) / K;
			WriteLine(ans);
		}
	}

	private long toId(long i, long j, long v) => (i * W + j) * 4 + v;

	private void push(long i, long j, long v, long x)
	{
		long id = toId(i, j, v);
		if(dist[id] <= x)
			return;

		dist[id] = x;
		pq.Push((x, id));
	}

	private long modCeil(long x) => ((x + K - 1) / K) * K;	
}

public class PriorityQueue<T>
{
	public long Count { get; private set; } = 0;
	public long MaxSize { get; private set; } = 0;
	private T[] m_heap;
	private Comparison<T> Comp = null;
	
	public PriorityQueue(long maxSize, Comparison<T> comp)
	{
		if(maxSize <= 0)
			throw new Exception();
		MaxSize = maxSize;
		m_heap = new T[maxSize];

		Comp = comp;
	}
	
	public void Push(T x)
	{
		if(Count == MaxSize)
		{
			T[] new_heap = new T[MaxSize << 1];
			Array.Copy(m_heap, new_heap, MaxSize);
			m_heap = new_heap;
			MaxSize <<= 1;
		}
		
		long i = Count++;
		while(i > 0)
		{
			long p = (i - 1)/2;
			if(Comp(m_heap[p], x) <= 0)
				break;
			m_heap[i] = m_heap[p];
			i = p;			
		}
		m_heap[i] = x;		
	}
	
	public T Pop()
	{
		if(Count == 0)
			throw new Exception("Queue is empty.");
		
		T result = m_heap[0];
		T x = m_heap[--Count];
		long i = 0;
		while(i * 2 + 1 < Count)
		{
			long c1 = i * 2 + 1, c2 = i * 2 + 2;
			if(c2 < Count && Comp(m_heap[c2], m_heap[c1]) < 0)
				c1 = c2;
			if(Comp(m_heap[c1], x) >= 0)
				break;
			m_heap[i] = m_heap[c1];
			i = c1;
		}
		m_heap[i] = x;
		
		return result;		
	}
	
	public T Peek() => m_heap[0];
}

public static class MyIO
{
	private static string[] args = new string[0];
	private static int cnt = 0;
	private static IEnumerable<string> getArgs(long N) => Range(0, N).Select(_ => getArg());
	private static string getArg()
	{
		if(cnt == args.Length) { args = Console.ReadLine().Split(); cnt = 0; }
		return args[cnt++];
	}

	public static int GetInt() => int.Parse(getArg());
	public static long GetLong() => long.Parse(getArg());
	public static double GetDouble() => double.Parse(getArg());
	public static decimal GetDecimal() => decimal.Parse(getArg());
	public static string GetString() => getArg();
	public static char GetChar() => getArg()[0];
	public static int[] GetInts(long N) => getArgs(N).Select(int.Parse).ToArray();
	public static long[] GetLongs(long N) => getArgs(N).Select(long.Parse).ToArray();
	public static double[] GetDoubles(long N) => getArgs(N).Select(double.Parse).ToArray();
	public static decimal[] GetDecimals(long N) => getArgs(N).Select(decimal.Parse).ToArray();
	public static string[] GetStrings(long N) => getArgs(N).ToArray();
}

public static class MyUtil
{
	public static void chmax<T>(ref T x, T y) where T : IComparable<T> { if(x.CompareTo(y) < 0) x = y; }
	public static void chmin<T>(ref T x, T y) where T : IComparable<T> { if(x.CompareTo(y) > 0)	x = y; }
	public static void swap<T>(ref T x, ref T y) { T tmp = x; x = y; y = tmp; }
	public static long rightShift(long x, long y) => (x >> (int)y);
	public static long leftShift(long x, long y) => (x << (int)y);
	public static bool contains(long s, long x) => (rightShift(s, x) & 1L) == 1L;
	public static long gcd(long x, long y) => (y == 0) ? x : gcd(y, x % y);
	public static long lcm(long x, long y) => (x / gcd(x,y)) * y;	
	public static IEnumerable<int> Range(long start, long count) => Enumerable.Range((int)start, (int)count);
	public static void Sort(this List<string> source) => source.Sort(StringComparer.Ordinal);
}


Measured memory_bytes: 73704