using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using static System.Math;
using System.Text;
using System.Threading;
using System.Globalization;
using System.Runtime.CompilerServices;
using Library;

namespace Program
{
    public static class ProblemF
    {
        static bool SAIKI = false;
        static public int numberOfRandomCases = 0;
        static public void MakeTestCase(List<string> _input, List<string> _output, ref Func<string[], bool> _outputChecker)
        {
        }
        static public void Solve()
        {
            var H = NN;
            var W = NN;
            var K = NN;
            var x1 = NN - 1;
            var y1 = NN - 1;
            var x2 = NN - 1;
            var y2 = NN - 1;
            var cList = NSList(H);
            var dp = new long[H, W];
            var q = new Queue<long>();
            var GETA = 1000000000L;
            q.Enqueue(x1 * GETA + y1);
            var dist = new long[H, W];
            for (var i = 0; i < H; i++)
                for (var j = 0; j < W; j++)
                    dist[i, j] = 1000000000000000000;
            dist[x1, y1] = 0;
            while (q.Count > 0)
            {
                var v = q.Dequeue();
                var nowX = v / GETA;
                var nowY = v % GETA;
                var thisDist = dist[nowX, nowY];
                var uek = K;
                var uex = nowX - 1;
                while (true)
                {
                    if (uek <= 0) break;
                    if (uex < 0) break;
                    if (cList[uex][(int)nowY] == '@') break;
                    if (dist[uex, nowY] > thisDist + 1)
                    {
                        dist[uex, nowY] = thisDist + 1;
                        q.Enqueue(uex * GETA + nowY);
                    }
                    else if (dist[uex, nowY] < thisDist + 1) break;
                    --uek;
                    --uex;
                }
                var shitak = K;
                var shitax = nowX + 1;
                while (true)
                {
                    if (shitak <= 0) break;
                    if (shitax >= H) break;
                    if (cList[shitax][(int)nowY] == '@') break;
                    if (dist[shitax, nowY] > thisDist + 1)
                    {
                        dist[shitax, nowY] = thisDist + 1;
                        q.Enqueue(shitax * GETA + nowY);
                    }
                    else if (dist[shitax, nowY] < thisDist + 1) break;
                    --shitak;
                    ++shitax;
                }
                var migik = K;
                var migiy = nowY + 1;
                while (true)
                {
                    if (migik <= 0) break;
                    if (migiy >= W) break;
                    if (cList[nowX][(int)migiy] == '@') break;
                    if (dist[nowX, migiy] > thisDist + 1)
                    {
                        dist[nowX, migiy] = thisDist + 1;
                        q.Enqueue(nowX * GETA + migiy);
                    }
                    else if (dist[nowX, migiy] < thisDist + 1) break;
                    --migik;
                    ++migiy;
                }
                var hidarik = K;
                var hidariy = nowY - 1;
                while (true)
                {
                    if (hidarik <= 0) break;
                    if (hidariy < 0) break;
                    if (cList[nowX][(int)hidariy] == '@') break;
                    if (dist[nowX, hidariy] > thisDist + 1)
                    {
                        dist[nowX, hidariy] = thisDist + 1;
                        q.Enqueue(nowX * GETA + hidariy);
                    }
                    else if (dist[nowX, hidariy] < thisDist + 1) break;
                    --hidarik;
                    --hidariy;
                }
            }
            if (dist[x2, y2] == 1000000000000000000) Console.WriteLine(-1);
            else Console.WriteLine(dist[x2, y2]);
        }
        class Printer : StreamWriter
        {
            public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
            public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { base.AutoFlush = false; }
            public Printer(Stream stream, Encoding encoding) : base(stream, encoding) { base.AutoFlush = false; }
        }
        static LIB_FastIO fastio = new LIB_FastIODebug();
        static public void Main(string[] args) { if (args.Length == 0) { fastio = new LIB_FastIO(); Console.SetOut(new Printer(Console.OpenStandardOutput())); } if (SAIKI) { var t = new Thread(Solve, 134217728); t.Start(); t.Join(); } else Solve(); Console.Out.Flush(); }
        static long NN => fastio.Long();
        static double ND => fastio.Double();
        static string NS => fastio.Scan();
        static long[] NNList(long N) => Repeat(0, N).Select(_ => NN).ToArray();
        static double[] NDList(long N) => Repeat(0, N).Select(_ => ND).ToArray();
        static string[] NSList(long N) => Repeat(0, N).Select(_ => NS).ToArray();
        static long Count<T>(this IEnumerable<T> x, Func<T, bool> pred) => Enumerable.Count(x, pred);
        static IEnumerable<T> Repeat<T>(T v, long n) => Enumerable.Repeat<T>(v, (int)n);
        static IEnumerable<int> Range(long s, long c) => Enumerable.Range((int)s, (int)c);
        static IOrderedEnumerable<T> OrderByRand<T>(this IEnumerable<T> x) => Enumerable.OrderBy(x, _ => xorshift);
        static IOrderedEnumerable<T> OrderBy<T>(this IEnumerable<T> x) => Enumerable.OrderBy(x.OrderByRand(), e => e);
        static IOrderedEnumerable<T1> OrderBy<T1, T2>(this IEnumerable<T1> x, Func<T1, T2> selector) => Enumerable.OrderBy(x.OrderByRand(), selector);
        static IOrderedEnumerable<T> OrderByDescending<T>(this IEnumerable<T> x) => Enumerable.OrderByDescending(x.OrderByRand(), e => e);
        static IOrderedEnumerable<T1> OrderByDescending<T1, T2>(this IEnumerable<T1> x, Func<T1, T2> selector) => Enumerable.OrderByDescending(x.OrderByRand(), selector);
        static IOrderedEnumerable<string> OrderBy(this IEnumerable<string> x) => x.OrderByRand().OrderBy(e => e, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<T> OrderBy<T>(this IEnumerable<T> x, Func<T, string> selector) => x.OrderByRand().OrderBy(selector, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<string> OrderByDescending(this IEnumerable<string> x) => x.OrderByRand().OrderByDescending(e => e, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<T> OrderByDescending<T>(this IEnumerable<T> x, Func<T, string> selector) => x.OrderByRand().OrderByDescending(selector, StringComparer.OrdinalIgnoreCase);
        static uint xorshift { get { _xsi.MoveNext(); return _xsi.Current; } }
        static IEnumerator<uint> _xsi = _xsc();
        static IEnumerator<uint> _xsc() { uint x = 123456789, y = 362436069, z = 521288629, w = (uint)(DateTime.Now.Ticks & 0xffffffff); while (true) { var t = x ^ (x << 11); x = y; y = z; z = w; w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)); yield return w; } }
    }
}
namespace Library {
    class LIB_FastIO
    {
        public LIB_FastIO() { str = Console.OpenStandardInput(); }
        readonly Stream str;
        readonly byte[] buf = new byte[1024];
        int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }
        byte read()
        {
            if (isEof) throw new EndOfStreamException();
            if (ptr >= len)
            {
                ptr = 0;
                if ((len = str.Read(buf, 0, 1024)) <= 0)
                {
                    isEof = true;
                    return 0;
                }
            }
            return buf[ptr++];
        }
        char Char()
        {
            byte b = 0;
            do b = read();
            while (b < 33 || 126 < b);
            return (char)b;
        }
        virtual public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        virtual public long Long()
        {
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != '-' && (b < '0' || '9' < b));
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        virtual public double Double() { return double.Parse(Scan(), CultureInfo.InvariantCulture); }
    }
    class LIB_FastIODebug : LIB_FastIO
    {
        Queue<string> param = new Queue<string>();
        string NextString() { if (param.Count == 0) foreach (var item in Console.ReadLine().Split(' ')) param.Enqueue(item); return param.Dequeue(); }
        public LIB_FastIODebug() { }
        public override string Scan() => NextString();
        public override long Long() => long.Parse(NextString());
        public override double Double() => double.Parse(NextString());
    }
}


Measured memory_bytes: 33668