#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<utility>
#include<queue>


using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

struct fast_io {
	fast_io(){
		std::cin.tie(nullptr);
		std::ios::sync_with_stdio(false);
	};
} fio;


int H, W, K;
vector<string> c;

int dijkstra(int sy, int sx, int gy, int gx){
	priority_queue<pair<int,pair<int,int>>,vector<pair<int,pair<int,int>>>,greater<pair<int,pair<int,int>>>> q;
	
	vector<vector<int>> used(H, vector<int>(W, 0));
	vector<vector<int>> used2(H, vector<int>(W, 0));
	vector<vector<int>> d(H, vector<int>(W, INF));
	
	d[sy][sx] = 0;
	q.push({0,{sy, sx}});
	
	while(!q.empty()){
		pair<int,pair<int,int>> p = q.top();q.pop();
		int x = p.second.second;
		int y = p.second.first;
		int cost = p.first;
		
		// cout<<"y = "<<y<<" x = "<<x<<" cost = "<<cost<<endl;
		
		if(d[y][x] < cost) continue;
		
		// if(y == gy && gx == x) return cost;
		
		// if(!(used[y][x] & 1)) {
		if(used[y][x] <= 100) {
			for(int i = x + 1; i < W; i++){
				if(c[y][i] == '@') break;
				
				int ncost = (i - x - 1)/K + 1;
				
				// used[y][i] |= 1;
				used[y][i]++;
				
				if(ncost + cost < d[y][i]) {
					d[y][i] = ncost + cost;
					// used[y][i] = 0;
					// used[y][i] &= 1;
					q.push({d[y][i], {y, i}});
				}
			}
			
			for(int i = x - 1; i >= 0; i--){
				if(c[y][i] == '@') break;
				
				int ncost = (x - i - 1)/K + 1;
				
				// used[y][i] |= 1;
				used[y][i]++;
				
				if(ncost + cost < d[y][i]) {
					d[y][i] = ncost + cost;
					// used[y][i] = 0;
					// used[y][i] &= 1;
					q.push({d[y][i], {y, i}});
				}
			}
		}
		
		// if(!(used[y][x] & 2)) {
		if(used2[y][x] <= 100) {
			for(int i = y + 1; i < H; i++){
				if(c[i][x] == '@') break;
				
				int ncost = (i - y - 1)/K + 1;
				
				// used[i][x] |= 2;
				used2[i][x]++;
				
				if(ncost + cost < d[i][x]) {
					d[i][x] = ncost + cost;
					used[i][x] = 0;
					q.push({d[i][x], {i, x}});
				}
			}
			
			for(int i = y - 1; i >= 0; i--){
				if(c[i][x] == '@') break;
				
				int ncost = (y - i - 1)/K + 1;
				
				// used[i][x] |= 2;
				used2[i][x]++;
				
				if(ncost + cost < d[i][x]) {
					d[i][x] = ncost + cost;
					used[i][x] = 0;
					q.push({d[i][x], {i, x}});
				}
			}
		}
	}
	
	return d[gy][gx];
	// exit(2);
	// return -1;
}

class union_find
{
	int  _setnum;
	vector<int> par, nume;
public:
	union_find(){
	}
	
	union_find(int x){
		par.resize(x);
		nume.resize(x);
		init();
	}
	
	~union_find(){
		//
		
	}
	
	void clear(){
		_setnum = 0;
		par.clear();
		nume.clear();
	}
	
	void init(){
		_setnum = par.size();
		for(int i = 0; i < par.size(); i++){
			par[i] = i;
			nume[i] = 1;
		}
	}
	
	void resize(int x){
		
		par.resize(x);
		nume.resize(x);
		init();
	}

	int find(int x){
		return par[x] == x ? x : par[x] = find(par[x]);
	}

	void unite(int x, int y){
		x = find(x);
		y = find(y);
	
		if(x == y)return;
		
		_setnum--;
		
		if(nume[x] > nume[y]) std::swap(x,y);
		
		par[x] = y;
		nume[y] += nume[x];
	}
	
	bool same(int x, int y){
		return find(x) == find(y);
	}
	
	int numel(int x){
		return nume[find(x)];
	}
	
	int size(){
		return par.size();
	}
	
	int setnum(){
		return _setnum;
	}
};

signed main(){
	cout<<fixed<<setprecision(10);
	
	int x1, y1, x2, y2;
	union_find uf;
	
	cin>>H>>W>>K;
	
	
	uf.resize(H * W);
	
	cin>>x1>>y1>>x2>>y2;
	
	x1--;
	y1--;
	x2--;
	y2--;
	
	c.resize(H);
	
	for(int i = 0; i < H; i++){
		cin>>c[i];
	}
	
	for(int i = 0; i < H; i++){
		for(int j = 0; j < W; j++){
			if(c[i][j] == '@') continue;
			
			if(i + 1 < H) {
				if(c[i+1][j] != '@') uf.unite(i * W + j, (i + 1) * W + j);
				// cout<<"<>"<<endl;
			}
			if(j + 1 < W) {
				if(c[i][j+1] != '@') uf.unite(i * W + j, i * W + j + 1);
				// cout<<"[]"<<endl;
			}
		}
	}
	
	// for(int i = 0; i < H; i++){
		// for(int j = 0; j < W; j++){
		 // cout<<uf.find(i * W + j)<<" ";	
		// }
		// cout<<endl;
	// }
	
	if(uf.same(x1 * W + y1, x2 * W + y2) == false) {
		cout<<-1<<endl;
		return 0;
	}
	
	cout<<dijkstra(x1, y1, x2, y2)<<endl;
	
	return 0;
}

Measured memory_bytes: 81764