#include <bits/stdc++.h>
using namespace std;
const int N=6e6+6;
int dx[] = {0,-1,0,1};
int dy[] = {-1,0,1,0};
int R,C,n;
int sx,sy,ex,ey;
string g[N];
struct nd{
	int stp,r,c;
	bool operator < (const nd &y) const{
		if(stp != y.stp) return stp<y.stp;
		return (r+c) < (y.r+y.c);
	}
};
vector<nd> dis[N];
vector<bool> vis[N];
struct nd2{
	int x,y;
	bool operator < (const nd2 &q) const{
		return dis[q.x][q.y] < dis[x][y];
	}
};
priority_queue<nd2> q;
int main(){
	scanf("%d%d%d",&R,&C,&n);
	scanf("%d%d%d%d",&sx,&sy,&ex,&ey);
	for(int i=1;i<=R;i++){
		dis[i].resize(C+1);
		vis[i].resize(C+1);
		cin>>g[i];
		g[i] = ' '+g[i];
		for(int j=1;j<=C;j++)
			dis[i][j] = nd{R+C+1,0,0};
	}
	dis[sx][sy] = nd{0,n,n};
	q.push(nd2{sx,sy});
	vis[sx][sy] = 1;
	while(q.size()){
		int x = q.top().x;
		int y = q.top().y;
		q.pop();
	//	printf("%d %d %d %d %d\n",x,y,dis[x][y].stp,dis[x][y].r,dis[x][y].c);
		if(x==ex && y==ey){
			printf("%d\n",dis[x][y].stp);
			return 0;
		}
		for(int i=0;i<4;i++){
			int xx = x+dx[i];
			int yy = y+dy[i];
			if(xx>R || yy>C || xx<1 || yy<1 || vis[xx][yy]) continue;
			nd t;
			if(dis[x][y].r==n && dis[x][y].c==n){
				if(g[xx][yy]=='.') t = dis[x][y];
				else t = nd{dis[x][y].stp+1,1,1};
			}
			else{
				t = dis[x][y];
				if(dx[i]) t.r++;
				if(dy[i]) t.c++;
				if(t.r>n || t.c>n) continue;
			}
			if(t < dis[xx][yy]){
				dis[xx][yy] = t;
				q.push(nd2{xx,yy});
				vis[xx][yy] = 1;
			}
		}
	}
	return 0;
}