#include <bits/stdc++.h>
using namespace std;
const int N=6e6+5,inf=0x3f3f3f3f;
int dx[] = {0,-1,0,1};
int dy[] = {-1,0,1,0};
int R,C,n,lay;
int sx,sy,ex,ey;
string g[N];
struct nd{int x,y;};
struct nd2{int lay,r,c;};
vector<nd2> f[N];
vector<int> vis[N];
int tim;
queue<nd> q[2];
int now=1,pre=0;
void dfs0(int x,int y){
	q[now].push(nd{x,y});
	f[x][y] = nd2{0,0,0};
	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) continue;
		if(f[xx][yy].lay!=inf || g[xx][yy]!='.') continue;
		dfs0(xx,yy);
	}
}
queue<nd> q2;
bool waste(nd2 me,nd2 he){
	if(me.lay != he.lay) return me.lay>he.lay;
	return me.r>=he.r && me.c>=he.c;
}
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++){
		cin>>g[i]; g[i]=' '+g[i];
		f[i].resize(C+1);
		vis[i].resize(C+1);
		for(int j=1;j<=C;j++)
			f[i][j].lay = inf;
	}
	dfs0(sx,sy);
	if(f[ex][ey].lay != inf) {puts("0"); return 0;}
	for(lay=1;;lay++){
		swap(now,pre);
		while(q[pre].size()){
			int X=q[pre].front().x, Y=q[pre].front().y;
			q[pre].pop();
			tim++;
			f[X][Y] = nd2{lay,0,0};
			vis[X][Y] = tim;
			q2.push(nd{X,Y});
			while(q2.size()){
				int x=q2.front().x, y=q2.front().y;
				nd2 t = f[x][y];
				q2.pop();
				for(int i=0;i<4;i++){
					int xx=x+dx[i],yy=y+dy[i];
					int rr=t.r+(dx[i]!=0),cc=t.c+(dy[i]!=0);
					if(xx>R || yy>C || xx<1 || yy<1) continue;
					if(vis[xx][yy] == tim) continue;
					if(waste(nd2{lay,rr,cc},f[xx][yy])) continue;
					if(g[xx][yy]=='#' && (t.r>=n||t.c>=n)) continue;

					if(f[xx][yy].lay == inf) q[now].push(nd{xx,yy});
					f[xx][yy] = nd2{lay,rr,cc};
					vis[xx][yy] = tim;
					q2.push(nd{xx,yy});
				}
			}
		}
		// printf("%d\n",lay);
		// for(int i=1;i<=R;i++){
		// 	for(int j=1;j<=C;j++){
		// 		if(f[i][j].lay == inf) printf("%c",g[i][j]);
		// 		else printf("%d",f[i][j].lay);
		// 	}
		// 	puts("");
		// }
		if(f[ex][ey].lay != inf) {printf("%d\n",lay); return 0;}
	}
	return 0;
}