#include <bits/stdc++.h>

using namespace std;

const int OO = 1e9;
const double EPS = 1e-9;

#define ndl cout << '\n'
#define sz(v) int(v.size())
#define pb push_back
#define mp make_pair
#define fs first
#define sc second
#define present(a, x) (a.find(x) != a.end())
#ifdef LOCAL
#define db(...) ({cout << "> Line " << __LINE__  \
		<< ": "; _db(#__VA_ARGS__, __VA_ARGS__);})
#define RNG() rng()
#else
#define db(...) true
#define RNG() true
#endif

template<class T>
void _db(const char *dbStr, T e) {
	cout << dbStr << " = " << e << endl;
}
template<class T, class... L>
void _db(const char *dbStr, T e, L... r) {
  while(*dbStr != ',') cout << *dbStr++;
  cout << " = " << e << ','; _db(dbStr + 1, r...);
}
template<class S, class T>
ostream& operator<<(ostream& o, const map<S, T>& v) {
	o << "["; int i = 0;
	for (const pair<S, T>& pr : v) o << (!i++ ? "" : ", ") << "{"
	<< pr.fs << " : " << pr.sc << "}"; return o << "]";
}
template<template <class, class...> class S, class T, class... L>
ostream& operator<<(ostream& o, const S<T, L...>& v) {
	o << "["; int i = 0;
	for (const auto& e : v) o << (!i++ ? "" : ", ") << e;
	return o << "]";
}
template<class S, class T>
ostream& operator<<(ostream& o, const pair<S, T>& pr) {
	return o << "(" << pr.fs << ", " << pr.sc << ")";
}
ostream& operator<<(ostream& o, const string& s) {
	for (const char& c : s) o << c;
	return o;
}

template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;
template<class T> using VVV = VV<V<T>>;
using ll = long long;
using pii = pair<int, int>;
using vi = V<int>;
using vii = V<pii>;
using vvi = VV<int>;
using mii = map<int, int>;
using umii = unordered_map<int, int>;
using si = set<int>;
using usi = unordered_set<int>;


const int MX = 1e6 + 5;
int H, W, K, sx, sy, tx, ty;
si rows[MX], cols[MX];
VV<char> grid;

void rmv(int r, int c) {
	rows[r].erase(c);
	cols[c].erase(r);
}


int main() {
	#ifdef LOCAL
	auto stTime = clock();
//	freopen("in.txt", "r", stdin);
	mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
	#endif
	ios::sync_with_stdio(false);
	cout.precision(10);
	cin.tie(0);

	cin >> H >> W >> K;

	cin >> sx >> sy >> tx >> ty;

	vvi dist(H + 1, vi(W + 1, OO));
	grid.assign(H + 1, V<char>(W + 1, 'x'));

	for (int i = 1; i <= H; ++i) {
		for (int j = 1; j <= W; ++j) {
			cin >> grid[i][j];
			rows[i].insert(j);
			cols[j].insert(i);
		}
	}
	queue<pii> q;
	q.push(mp(sx, sy));
	dist[sx][sy] = 0;
	rmv(sx, sy);

	while (!q.empty()) {
		pii pr = q.front();
		q.pop();
		int r = pr.fs, c = pr.sc;

		{
			auto it = rows[r].lower_bound(c);

			while (it != rows[r].end() && grid[r][*it] == '.' && abs(*it - c) <= K) {
				int cc = *it;
				dist[r][cc] = dist[r][c] + 1;
				++it;
				rmv(r, cc);
				q.push(mp(r, cc));
			}

			it = rows[r].lower_bound(c);
			if (it != rows[r].begin()) {
				--it;
				while (grid[r][*it] == '.' && abs(*it - c) <= K) {
					int cc = *it;
					dist[r][cc] = dist[r][c] + 1;
					q.push(mp(r, cc));
					if (it == rows[r].begin()) {
						rmv(r, cc);
						break;
					}
					--it;
					rmv(r, cc);
				}
			}
		}


		{
			auto it = cols[c].lower_bound(r);

			while (it != cols[c].end() && grid[*it][c] == '.' && abs(*it - r) <= K) {
				int rr = *it;
				dist[rr][c] = dist[r][c] + 1;
				++it;
				rmv(rr, c);
				q.push(mp(rr, c));
			}

			it = cols[c].lower_bound(r);
			if (it != cols[c].begin()) {
				--it;
				while (grid[*it][c] == '.' && abs(*it - r) <= K) {
					int rr = *it;
					dist[rr][c] = dist[r][c] + 1;
					q.push(mp(rr, c));
					if (it == cols[c].begin()) {
						rmv(rr, c);
						break;
					}
					--it;
					rmv(rr, c);
				}
			}
		}


	}

	if (dist[tx][ty] == OO)
		cout << "-1\n";
	else
		cout << dist[tx][ty] << '\n';


	#ifdef LOCAL
	cout << "\n\n\nExecution time: " <<
		(clock() - stTime) * 1e3 / CLOCKS_PER_SEC << " ms" << endl;
	#endif
	return 0;
}


Measured memory_bytes: 200436