import std.stdio, std.conv, std.functional, std.string;
import std.algorithm, std.array, std.container, std.range, std.typecons;
import std.bigint, std.numeric, std.math, std.random;
import core.bitop;

string FMT_F = "%.10f";

static File _f;
void file_io(string fn) { _f = File(fn, "r"); }
static string[] s_rd;
T _RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T _RD(T = long)(File f) { while(!s_rd.length) s_rd = f.readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T[] _RDA(T = long)(T fix = 0) { auto r = readln.chomp.split.to!(T[]); r[] += fix; return r; }
T[] _RDA(T = long)(File f, T fix = 0) { auto r = f.readln.chomp.split.to!(T[]); r[] += fix; return r; }
T RD(T = long)() { if (_f.isOpen) return _RD!T(_f); else return _RD!T; }
T[] RDA(T = long)(T fix = 0) { if (_f.isOpen)  return _RDA!T(_f, fix); else return _RDA!T(fix); }

size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

void chmin(T)(ref T x, T y) { x = min(x, y); } void chmax(T)(ref T x, T y) { x = max(x, y); }
bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
T lcm(T)(T x, T y) { return x * (y / gcd(x, y)); }

//long mod = 10^^9 + 7;
long mod = 998_244_353;
//long mod = 1_000_003;
void moda(T)(ref T x, T y) { x = (x + y) % mod; }
void mods(T)(ref T x, T y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(T)(ref T x, T y) { x = (x * y) % mod; }
void modpow(T)(ref T x, T y) { if (!y) { x = 1; return; } auto t = x; x.modpow(y>>1); x.modm(x); if (y&1) x.modm(t); }
void modd(T)(ref T x, T y) { y.modpow(mod - 2); x.modm(y); }

void main()
{
	auto H = RD;
	auto W = RD;
	auto K = RD;
	auto x1 = RD-1;
	auto y1 = RD-1;
	auto x2 = RD-1;
	auto y2 = RD-1;
	auto c = new string[](H);
	foreach (i; 0..H)
	{
		c[i] = RD!string;
	}

	long[][] open_l = [[x1, y1]], open_r = [[x1, y1]], open_t = [[x1, y1]], open_b = [[x1, y1]];
	auto used = new bool[][](H, W);
	used[x1][y1] = true;

	long ans = -1;
	long cnt = 1;
	(){
	while (true)
	{
		long[][] next_l, next_r, next_t, next_b;
		while (!open_l.empty)
		{
			auto nd = open_l.front; open_l.popFront;
			auto x  = nd[0];
			auto y  = nd[1];
			foreach (i; 1..K+1)
			{
				auto nx = x;
				auto ny = y-i;
				if (!inside(ny, 0, W)) break;
				if (c[nx][ny] == '@') break;
				if (used[nx][ny]) continue;
				used[nx][ny] = true;
				if (nx == x2 && ny == y2)
				{
					ans = cnt;
					return;
				}
				if (i == K)
				{
					next_l ~= [nx, ny];
				}
				next_t ~= [nx, ny];
				next_b ~= [nx, ny];
			}
		}
		while (!open_r.empty)
		{
			auto nd = open_r.front; open_r.popFront;
			auto x  = nd[0];
			auto y  = nd[1];
			foreach (i; 1..K+1)
			{
				auto nx = x;
				auto ny = y+i;
				if (!inside(ny, 0, W)) break;
				if (c[nx][ny] == '@') break;
				if (used[nx][ny]) continue;
				used[nx][ny] = true;
				if (nx == x2 && ny == y2)
				{
					ans = cnt;
					return;
				}
				if (i == K)
				{
					next_r ~= [nx, ny];
				}
				next_t ~= [nx, ny];
				next_b ~= [nx, ny];
			}
		}
		while (!open_t.empty)
		{
			auto nd = open_t.front; open_t.popFront;
			auto x  = nd[0];
			auto y  = nd[1];
			foreach (i; 1..K+1)
			{
				auto nx = x-i;
				auto ny = y;
				if (!inside(nx, 0, H)) break;
				if (c[nx][ny] == '@') break;
				if (used[nx][ny]) continue;
				used[nx][ny] = true;
				if (nx == x2 && ny == y2)
				{
					ans = cnt;
					return;
				}
				if (i == K)
				{
					next_t ~= [nx, ny];
				}
				next_l ~= [nx, ny];
				next_r ~= [nx, ny];
			}
		}
		while (!open_b.empty)
		{
			auto nd = open_b.front; open_b.popFront;
			auto x  = nd[0];
			auto y  = nd[1];
			foreach (i; 1..K+1)
			{
				auto nx = x+i;
				auto ny = y;
				if (!inside(nx, 0, H)) break;
				if (c[nx][ny] == '@') break;
				if (used[nx][ny]) continue;
				used[nx][ny] = true;
				if (nx == x2 && ny == y2)
				{
					ans = cnt;
					return;
				}
				if (i == K)
				{
					next_b ~= [nx, ny];
				}
				next_l ~= [nx, ny];
				next_r ~= [nx, ny];
			}
		}
		++cnt;
		if (next_l.empty && next_r.empty && next_t.empty && next_b.empty)
		{
			return;
		}
		open_l = next_l;
		open_r = next_r;
		open_t = next_t;
		open_b = next_b;
	}}();

	writeln(ans);
	stdout.flush;
	debug readln;
}


Measured memory_bytes: 50788