using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        Console.SetOut(sw);
        Solve();
        Console.Out.Flush();
    }
    static void Solve()
    {
        checked
        {
            var H = sc.ReadInt();
            var W = sc.ReadInt();
            var K = sc.ReadLong();
            var k2 = K * K;
            var sh = sc.ReadInt() - 1;
            var sw = sc.ReadInt() - 1;
            var eh = sc.ReadInt() - 1;
            var ew = sc.ReadInt() - 1;
            var S = new string[H];
            for (int i = 0; i < H; i++)
            {
                S[i] = sc.ReadStr();
            }
            var inf = long.MaxValue / 2;
            var dp = new long[H, W, 4];
            for (int i = 0; i < H; i++)
            {
                for (int j = 0; j < W; j++)
                {
                    for (int k = 0; k < 4; k++)
                    {
                        dp[i, j, k] = inf;
                    }
                }
            }
            Comparison<(long, int, int, int, int)> f = (x, y) => x.Item1.CompareTo(y.Item1);
            var pq = new PriorityQueue<(long, int, int, int, int)>(false, Comparer<(long, int, int, int, int)>.Create(f));
            pq.Enqueue((0L, -1, 0, sh, sw));
            while (pq.Count > 0)
            {
                var (dist, dir, k, h, w) = pq.Dequeue();
                if (dir != -1 && dp[h, w, dir] != dist) continue;

                var dh = new int[] { -1, 0, 1, 0 };
                var dw = new int[] { 0, -1, 0, 1 };
                for (int d = 0; d < 4; d++)
                {
                    var nh = h + dh[d];
                    var nw = w + dw[d];
                    if (0 <= nh && nh < H && 0 <= nw && nw < W)
                    {
                        if (S[nh][nw] == '@') continue;
                        int nk;
                        long ndist;
                        if (dir == d)
                        {
                            // 同じ方向に進む
                            ndist = dist + 1;
                            nk = k + 1;
                            if (nk == K + 1)
                            {
                                // すでにKマス進んでいる
                                nk = 1;
                            }
                        }
                        else
                        {
                            // 方向転換して進む
                            ndist = (dist + K - 1) / K * K + 1;
                            nk = 1;
                        }
                        if (dp[nh, nw, d] <= ndist) continue;
                        dp[nh, nw, d] = ndist;
                        pq.Enqueue((ndist, d, nk, nh, nw));
                    }
                }
            }
            var ans = inf;
            for (int i = 0; i < 4; i++)
            {
                ans = Math.Min(ans, dp[eh, ew, i]);
            }
            if (ans == inf) ans = -1;
            else ans = (ans + K - 1) / K;
            Console.WriteLine(ans);
        }
    }
    // Comparison<T> f = (x, y) => x.CompareTo(y);
    // Comparer<T>.Create(f)
    class PriorityQueue<T>
    {
        public int Count;
        private int Capacity;
        private bool IsMaxHeap;
        private T[] Buffer;
        private IComparer<T> Cmp;
        public PriorityQueue(bool isMaxHeap = true, IComparer<T> cmp = null)
        {
            Count = 0;
            Capacity = 1 << 10;
            IsMaxHeap = isMaxHeap;
            Buffer = new T[Capacity];
            if (cmp != null) Cmp = cmp;
            else Cmp = Comparer<T>.Default;
        }
        public PriorityQueue(int capacity, bool isMaxHeap = true, IComparer<T> cmp = null)
        {
            Count = 0;
            Capacity = Math.Max(16, capacity);
            IsMaxHeap = isMaxHeap;
            Buffer = new T[Capacity];
            if (cmp != null) Cmp = cmp;
            else Cmp = Comparer<T>.Default;
        }
        private void Resize()
        {
            Capacity <<= 1;
            Array.Resize(ref Buffer, Capacity);
        }
        public void Enqueue(T value)
        {
            if (Count == Capacity) Resize();
            Buffer[Count] = value;
            Count++;
            UpHeap();
        }
        public T Dequeue()
        {
            var res = Buffer[0];
            Swap(0, Count - 1);
            Count--;
            DownHeap();
            return res;
        }
        public T Peek() { return Buffer[0]; }
        private void Swap(int i, int j)
        {
            var tmp = Buffer[i];
            Buffer[i] = Buffer[j];
            Buffer[j] = tmp;
        }
        private void UpHeap()
        {
            var n = this.Count - 1;
            while (n != 0)
            {
                var parent = (n - 1) / 2;
                if (Compare(Buffer[n], Buffer[parent]) > 0)
                {
                    Swap(n, parent);
                    n = parent;
                }
                else break;
            }
        }
        private void DownHeap()
        {
            var parent = 0;
            while (true)
            {
                var child = 2 * parent + 1;
                if (child > this.Count - 1) break;
                if (child < Count - 1 && Compare(Buffer[child], Buffer[child + 1]) < 0)
                {
                    child += 1;
                }
                if (Compare(Buffer[parent], Buffer[child]) < 0)
                {
                    Swap(parent, child);
                    parent = child;
                }
                else break;
            }
        }
        private int Compare(T x, T y)
        {
            var res = Cmp.Compare(x, y);
            if (!IsMaxHeap) res *= -1;
            return res;
        }
    }
    static Scanner sc = new Scanner();
}
class Scanner
{
    string[] S = new string[0];
    int Index = 0;
    char[] Separators = new char[] { ' ' };

    public string Next()
    {
        if (this.Index < this.S.Length) return this.S[this.Index++];
        var line = "";
        while (line == "") line = Console.ReadLine();
        this.S = line.Split(this.Separators, StringSplitOptions.RemoveEmptyEntries);
        if (this.S.Length == 0) return this.Next();
        this.Index = 0;
        return this.S[this.Index++];
    }
    public string ReadStr()
    {
        return this.Next();
    }
    public char ReadChar()
    {
        return this.Next()[0];
    }
    public int ReadInt()
    {
        return int.Parse(this.Next());
    }
    public uint ReadUInt()
    {
        return uint.Parse(this.Next());
    }
    public long ReadLong()
    {
        return long.Parse(this.Next());
    }
    public double ReadDouble()
    {
        return double.Parse(this.Next());
    }
    public Tuple<int, int> ReadTup(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add);
    }
    public Tuple<long, long> ReadTupLong(int add = 0)
    {
        return Tuple.Create(this.ReadLong() + add, this.ReadLong() + add);
    }
    public Tuple<int, int, int> ReadTup3(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add);
    }
    public Tuple<int, int, int, int> ReadTup4(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add);
    }
    public int[] ReadIntArray(int n)
    {
        var array = new int[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadInt();
        }
        return array;
    }
    public long[] ReadLongArray(int n)
    {
        var array = new long[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadLong();
        }
        return array;
    }
    public double[] ReadDoubleArray(int n)
    {
        var array = new double[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadDouble();
        }
        return array;
    }
    public char[] ReadCharArray(int n)
    {
        var array = new char[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadChar();
        }
        return array;
    }
    public string[] ReadStrArray(int n)
    {
        var array = new string[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadStr();
        }
        return array;
    }
    public Tuple<long, long>[] ReadTupLongArray(int n, int add = 0)
    {
        var array = new Tuple<long, long>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTupLong(add);
        }
        return array;
    }
    public Tuple<int, int>[] ReadTupArray(int n, int add = 0)
    {
        var array = new Tuple<int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup(add);
        }
        return array;
    }
    public Tuple<int, int, int>[] ReadTup3Array(int n, int add = 0)
    {
        var array = new Tuple<int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup3(add);
        }
        return array;
    }
    public Tuple<int, int, int, int>[] ReadTup4Array(int n, int add = 0)
    {
        var array = new Tuple<int, int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup4(add);
        }
        return array;
    }
}


Measured memory_bytes: 91372