#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("unroll-loops")
//#pragma warning(disable : 4996)

#ifdef _MSC_VER
#include <intrin.h>
#define __builtin_popcount __popcnt
#define __builtin_popcountll __popcnt64
#endif

#include <limits.h>
#include <math.h>
#include <time.h>

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n - 1; i >= 0; --i)
#define FOR(i, m, n) for (int i = m; i < n; ++i)
#define FORR(i, m, n) for (int i = m - 1; i >= n; --i)
#define SORT(v, n) sort(v, v + n);
#define VSORT(v) sort(v.begin(), v.end());
#define REVERSE(v, n) reverse(v, v + n);
#define VREVERSE(v) reverse(v.begin(), v.end())
#define ll long long
#define print(x) cout << (x) << '\n'
#define pe(x) cout << (x) << " "
#define DEBUG(x) cout << #x << ": " << x << endl
#define lb(v, n) lower_bound(v.begin(), v.end(), (n))
#define ub(v, n) upper_bound(v.begin(), v.end(), (n))
//#define int long long
#define double long double
#define all(x) (x).begin(), (x).end()
#define print_space(v) REP(i, v.size()) cout << v[i] << ((i == v.size() - 1) ? "\n" : " ")
template <typename T1, typename T2> inline void chmin(T1& a, T2 b) {
	if (a > b) a = b;
}
template <typename T1, typename T2> inline void chmax(T1& a, T2 b) {
	if (a < b) a = b;
}
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef array<int, 3> arr3;
std::random_device rd;
std::mt19937 mt(rd());
constexpr ll MOD = 998244353;
constexpr int MAX = 500050;
const double pi = acos(-1);
constexpr double EPS = 1e-8;
constexpr ll LINF = 1e18 + 1;
constexpr int INF = 1e9 + 1;



int H, W, K;
void solve() {
	cin >> H >> W >> K;
	int sx, sy, gx, gy; cin >> sx >> sy >> gx >> gy;
	sx--, sy--, gx--, gy--;
	vector<vector<char>>c(H, vector<char>(W));
	vector<set<int>>row(H), col(W);
	vector<vector<int>>dist(H, vector<int>(W, INF));
	REP(i, H) {
		REP(j, W) {
			cin >> c[i][j];
		}
	}
	dist[sx][sy] = 0;

	REP(i, H) {
		FOR(j, -1, W+1) {
			row[i].insert(j);
		}
	}
	REP(j, W) {
		FOR(i, -1, H + 1) {
			col[j].insert(i);
		}
	}
	row[sx].erase(sy);
	col[sy].erase(sx);
	//priority_queue<arr3, vector<arr3>, greater<arr3>>que;
	queue<arr3>que;
	que.push({ sx,sy,0 });
	//print("a");
	//vector<int>errx, erry;
	while (!que.empty()) {
		arr3 arr = que.front(); que.pop();
		int x = arr[0], y = arr[1], res = arr[2];
		if (res > dist[x][y])continue;
		int nx = x;
		auto itrx = col[y].lower_bound(x);
		//DEBUG(x);
		//DEBUG(y);
		//errx.clear(), erry.clear();
		itrx--;
		nx = *itrx;
		while (nx >= x - K) {
			//DEBUG(nx);
			if (nx == -1)break;
			if (c[nx][y] == '@')break;

			if (dist[nx][y] > dist[x][y] + 1) {
				dist[nx][y] = dist[x][y] + 1;
				que.push({ nx,y,dist[nx][y] });
			}
			itrx=col[y].erase(itrx);
			itrx--;
			nx = *itrx;
		}
		itrx = col[y].lower_bound(x);
		nx = *itrx;
		while (nx <= x + K&&itrx!=col[y].end()) {
			//DEBUG(nx);
			if (nx == H)break;
			if (c[nx][y] == '@')break;
			if (dist[nx][y] > dist[x][y]+1) {
				dist[nx][y] = dist[x][y] + 1;
				que.push({ nx,y,dist[nx][y] });
			}
			itrx = col[y].erase(itrx);
			nx = *itrx;
		}
		int ny = y;
		auto itry = row[x].lower_bound(y);

		//errx.clear(), erry.clear();
		itry--;
		ny = *itry;
		while (ny >= y - K) {
			//DEBUG(ny);
			if (ny == -1)break;
			if (c[x][ny] == '@')break;
			if (dist[x][ny] > dist[x][y] + 1) {
				dist[x][ny] = dist[x][y] + 1;
				que.push({ x,ny,dist[x][ny] });
			}
			itry=row[x].erase(itry);
			itry--;
			ny = *itry;
			//print("done");
		}
		itry = row[x].lower_bound(y);
		ny = *itry;
		while (ny <= y + K) {
			//DEBUG(ny);
			if (ny == W)break;
			if (c[x][ny] == '@')break;
			if (dist[x][ny] > dist[x][y] + 1) {
				dist[x][ny] = dist[x][y] + 1;
				que.push({ x,ny,dist[x][ny] });
			}
			itry = row[x].erase(itry);
			ny = *itry;
		}
	}
	if (dist[gx][gy] == INF)print(-1);
	else print(dist[gx][gy]);
}




signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	//mt.seed((int)(time(0)));
	//REP(_, 10000)test();
	//int q;
	//cin >> q;
	//while (q--)
	solve();
}



Measured memory_bytes: 242532