#include <iostream>
#include <vector>
#include <deque>
#include <algorithm>
#include <numeric>
#include <string>
#include <cstring>
#include <list>
#include <unordered_set>
#include <tuple>
#include <cmath>
#include <limits>
#include <type_traits>
#include <iomanip>
#include <map>
#include <unordered_map>
#include <queue>
#include <stack>
#include <set>
#include <bitset>
#include <complex>
#include <regex>
#include <random>
using namespace std;

#define rep(i,n)	for(lint i = 0; i < n; i++)
#define repr(i,n)	for(lint i = n - 1; i >= 0; i--)
#define repi(i,ini,n)	for(lint i = ini; i < n; i++)
#define repir(i,ini,n)	for(lint i = n-1; i >= ini; i--)
#define repb(i,start,end)	for(lint i = start; i <= end; i++)
#define repbr(i,start,end)	for(lint i = end; i >= start; i--)

#define bit(n)				(1LL << (n))

#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define rg(v, ini, end) v.begin() + ini, v.begin()+end

#define ret return 0;
#define chmax(a, b) a=max(a,b)
#define chmin(a, b) a=min(a,b)

using lint = long long;
using ulint = unsigned long long;
using ld = long double;
struct xy
{
	lint x, y;
	xy() :x(0), y(0) {}
	xy(lint _x, lint _y) : x(_x), y(_y) {}
	xy operator+(const xy& p) const
	{
		return xy(x + p.x, y + p.y);
	}
	bool operator<(xy p) const
	{
		if (y == p.y)
			return x < p.x;
		return y < p.y;
	}
};
struct xyd
{
	ld x, y;
	xyd() :x(0), y(0) {}
	xyd(long double _x, long double _y) : x(_x), y(_y) {}
};
using vec = vector<lint>;
using vecd = vector<ld>;
using vecs = vector<string>;
using vecp = vector<xy>;
template<class T> using vect = vector<T>;
class vec2 : public vector<vector<lint>>
{
public:
	vec2() {}
	vec2(lint n) : vector(n) {}
	vec2(lint h, lint w) : vector(h, vector<lint>(w)) {}
	vec2(lint h, lint w, lint v) : vector(h, vector<lint>(w, v)) {}
};

template<class T> using priq = priority_queue<T>;
template<class T> using rpriq = priority_queue<T, vector<T>, greater<T>>;
template<class Key, class Val> using hashmap = unordered_map<Key, Val>;
template<class Key> using hashset = unordered_set<Key>;

mt19937 mtrand((random_device())());

const double pi = 3.141592653589793238462;
const lint intmax = 9223372036854775807;
const lint inf = 1100100100100100100LL;

constexpr lint div2(lint p, lint q)
{
	return (p + q - 1) / q;
}

#if(__cplusplus < 201703L)

	lint gcd(lint a, lint b) {
		while (1) {
			if (a < b) swap(a, b);
			if (!b) break;
			a %= b;
		}
		return a;
	}

	lint lcm(lint a, lint b)
	{
		return a / gcd(a, b) * b;
	}

#endif

template<class T>
struct nval {
	lint n;		// counts
	T val;
	nval() : n(0) {};
	nval(lint _n, T _val) : n(_n), val(_val) {};
};

template<class It, class It2>
auto spacel(It i, It2 end)
{
	if (i + 1 == end)
	{
		return '\n';
	}
	else
	{
		return ' ';
	}
}

ostream& setp(ostream& ost)
{
	cout << setprecision(60) << fixed;
	return ost;
}

const ulint mod = 1000000007;
//const ulint mod = 998244353;
const ld eps = 0.0000001;


lint h, w, k;

struct graph
{
	struct R
	{
		lint to, c;
		bool f;
	};

	lint v, e;

	vector<vector<R>> gr;

	graph(lint _v) : v(_v), e(0), gr(v)
	{}

	void add_e(lint from, lint to, lint cost, bool f = false)
	{
		gr[from].push_back({ to, cost, f });
		e++;
	}

	auto dijkstra(lint start)
	{
		vector<lint> d(v, inf);

		d[start] = 0;

		struct Vc
		{
			lint pos, d;
			bool operator<(const Vc& p) const
			{
				return d > p.d;
			}
		};

		priority_queue<Vc> que;
		que.push({ start, 0 });

		while (!que.empty())
		{
			auto vc = que.top();
			que.pop();

			rep(i, gr[vc.pos].size())
			{
				lint nc = vc.d + gr[vc.pos][i].c;
				if (gr[vc.pos][i].f)
					nc = div2(nc, k) * k;
				if (nc < d[gr[vc.pos][i].to])
				{
					d[gr[vc.pos][i].to] = nc;
					que.push({ gr[vc.pos][i].to, d[gr[vc.pos][i].to] });
				}
			}
		}

		return d;
	}

};

lint f(lint x, lint y, lint d)
{
	return h * w * d + w * y + x;
}

template<class Tv, class Tl, class Tr>
bool between(Tv val, Tl l, Tr r)
{
	return (val >= l) && (val <= r);
}

int main()
{
	cin >> h >> w >> k;
	xy p1, p2;
	cin >> p1.y >> p1.x >> p2.y >> p2.x;
	p1.x--; p1.y--; p2.x--; p2.y--;
	vecs c(h);
	rep(i, h)
		cin >> c[i];

	auto is = [&](lint x, lint y)
	{
		if (!between(x, 0, w - 1) || !between(y, 0, h - 1) || c[y][x] == '@')
			return false;
		return true;
	};

	graph g(4 * h * w);

	rep(i, h)
		rep(j, w)
	{
		if (is(j + 1, i))
		{
			g.add_e(f(j, i, 0), f(j + 1, i, 0), 1);
		}
		if (is(j - 1, i))
		{
			g.add_e(f(j, i, 1), f(j - 1, i, 1), 1);
		}
		if (is(j, i + 1))
		{
			g.add_e(f(j, i, 2), f(j, i + 1, 2), 1);
		}
		if (is(j, i - 1))
		{
			g.add_e(f(j, i, 3), f(j, i - 1, 3), 1);
		}

		rep(di, 4)
			rep(dj, 4)
		{
			g.add_e(f(j, i, di), f(j, i, dj), 0, true);
		}
	}

	lint ans = inf;
	//rep(i, 4)
	{
		auto d = g.dijkstra(f(p1.x, p1.y, 0));
		rep(j, 4)
		{
			chmin(ans, d[f(p2.x, p2.y, j)]);
		}
	}

	if (ans == inf)
	{
		cout << -1 << endl;
		ret;
	}

	cout << div2(ans, k) << endl;
	
	return 0;
}


Measured memory_bytes: 838352