#include <bits/stdc++.h>
using namespace std;
using ll = int_fast64_t;
const int mod = 1e9 + 7;
const int inf = (1 << 30) - 1;
const ll infll = (1LL << 61) - 1;
#define fast() ios::sync_with_stdio(false), cin.tie(nullptr)

template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s)
{
	return '"' + s + '"';
}

string to_string(const char *s)
{
	return to_string((string)s);
}

string to_string(bool b)
{
	return (b ? "true" : "false");
}

string to_string(vector<bool> v)
{
	bool first = true;
	string res = "{";
	for (int i = 0; i < static_cast<int>(v.size()); i++)
	{
		if (!first)
		{
			res += ", ";
		}
		first = false;
		res += to_string(v[i]);
	}
	res += "}";
	return res;
}

template <size_t N>
string to_string(bitset<N> v)
{
	string res = "";
	for (size_t i = 0; i < N; i++)
	{
		res += static_cast<char>('0' + v[i]);
	}
	return res;
}

template <typename A>
string to_string(A v)
{
	bool first = true;
	string res = "{";
	for (const auto &x : v)
	{
		if (!first)
		{
			res += ", ";
		}
		first = false;
		res += to_string(x);
	}
	res += "}";
	return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p)
{
	return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p)
{
	return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p)
{
	return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T)
{
	cerr << " " << to_string(H);
	debug_out(T...);
}

int main()
{
	fast();

	using P = pair<int, int>;

	// d[0] : うえ, d[1] : みぎ, d[2] : した, d[3] : ひだり
	int dx[] = {-1, 0, 1, 0}, dy[] = {0, 1, 0, -1};
	int H, W, K;
	cin >> H >> W >> K;
	vector<string> grid(H);
	vector<vector<vector<P>>> d(H);

	int sx, sy, gx, gy;

	cin >> sx >> sy >> gx >> gy;
	sx--, sy--, gx--, gy--;

	for (int i = 0; i < H; i++)
	{
		cin >> grid[i];
	}

	for (int i = 0; i < H; i++) // init
	{
		d[i] = vector<vector<P>>(W, vector<P>(4, P(inf, inf)));
	}

	// (最短距離, その方向に進んだ回数), (x, y), dir
	deque<pair<P, int>> que;
	for (int i = 0; i < 4; i++)
	{
		d[sx][sy][i] = P(1, 0);
		que.push_back({P(sx, sy), i});
	}

	while (!que.empty())
	{
		auto v = que.front();
		que.pop_front();
		int vx = v.first.first, vy = v.first.second, dir = v.second;

		for (int i = 0; i < 4; i++) // 向きを変える
		{
			if (i == dir)
				continue;
			P ncost = make_pair(d[vx][vy][dir].first + 1, 0);

			if (d[vx][vy][i] <= ncost)
				continue;

			d[vx][vy][i] = ncost;

			que.push_back({P(vx, vy), i});
		}

		// 直進する
		int nx = vx + dx[dir], ny = vy + dy[dir];

		if (nx < 0 || nx >= H || ny < 0 || ny >= W) // grid の外
			continue;
		if (grid[nx][ny] == '@') // 行き止まり
			continue;

		int df = d[vx][vy][dir].first, ds = d[vx][vy][dir].second;
		P ncost = make_pair(df + (ds + 1) / (K + 1), ds % K + 1);
		if (d[nx][ny][dir] <= ncost)
			continue;
		d[nx][ny][dir] = ncost;

		if (ds >= K)
			que.push_back({P(nx, ny), dir});
		else
			que.push_front({P(nx, ny), dir});
	}

	int min_cost = (*min_element(d[gx][gy].begin(), d[gx][gy].end())).first;

	cout << (min_cost == inf ? -1 : min_cost) << "\n";
}


Measured memory_bytes: 79056