#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
using namespace std;

#define ALL(v) begin(v),end(v)
typedef pair<int,int> pii;

int solve(){
	ios::sync_with_stdio(false);
	
	int h, w, k, r1, c1, r2, c2;
	cin >> h >> w >> k >> r1 >> c1 >> r2 >> c2;
	vector<vector<int>> vis(h + 2, vector<int>(w + 2, 15));
	for(int i = 0; i < h; ++i){
		string s;
		cin >> s;
		for(int j = 0; j < w; ++j){
			if(s[j] == '.'){ vis[i + 1][j + 1] = 0; }
		}
	}
	vector<pii> curr, nxt;
	auto process = [&](int dy, int dx, int f){
		for(const auto &p : curr){
			for(int i = 1; i <= k; ++i){
				int y = p.first + dy * i;
				int x = p.second + dx * i;
				if(vis[y][x] & f){ break; }
				vis[y][x] |= f;
				nxt.emplace_back(y, x);
			}
		}
	};
	nxt.emplace_back(r1, c1);
	for(int tm = 0; !nxt.empty(); ++tm){
		curr.swap(nxt);
		nxt.clear();
		sort(ALL(curr));
		curr.erase(unique(ALL(curr)), curr.end());
		for(const auto &p : curr){
			if(p.first == r2 && p.second == c2){
				return tm;
			}
			vis[p.first][p.second] = 15;
		}
		process(-1, 0, 1);
		reverse(ALL(curr));
		process(1, 0, 2);
		sort(ALL(curr), [](const pii &p, const pii &q){ return p.second < q.second; });
		process(0, -1, 4);
		reverse(ALL(curr));
		process(0, 1, 8);
	}
	return -1;
}

int main(){
	cout << solve() << '\n';
}
