#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;
int sx,sy,ex,ey;
string g[N];
struct nd2{int lay,r,c;};
bool waste(nd2 me,nd2 he){
	if(he.lay != me.lay) return he.lay<me.lay;
	return he.r<=me.r && he.c<me.c;
}
vector<nd2> f[N];
vector<int> vis[N];
struct nd{int x,y;};
queue<nd> q[2];
int now=1,pre,lay=1,tim;
void dfs0(int x,int y){
	if(f[x][y].lay != inf) return;
	f[x][y] = nd2{1,0,0};
	q[now].push(nd{x,y});
	for(int i=0;i<4;i++){
		int xx=x+dx[i],yy=y+dy[i];
		if(xx>R || yy>C || xx<1 || yy<1) continue;
		if(g[xx][yy] == '#') continue;
		dfs0(xx,yy);
	}
}
void dfs(int x,int y,int r,int c){
	if(waste(nd2{lay,r,c},f[x][y])) return;
	if(vis[x][y] == tim) return;
	cout<<x<<' '<<y<<' '<<r<<' '<<c<<endl;
	vis[x][y] = tim; 
	if(f[x][y].lay==inf)
		q[now].push(nd{x,y});
	f[x][y] = nd2{lay,r,c};
	for(int i=0;i<4;i++){
		int xx=x+dx[i],yy=y+dy[i];
		int rr=r+(dx[i]!=0),cc=c+(dy[i]!=0);
		if(xx>R || yy>C || xx<1 || yy<1) continue;
		if(rr>n || cc>n){
			if(g[xx][yy] == '.') dfs(xx,yy,rr,cc);
		}
		else dfs(xx,yy,rr,cc);
	}
}
queue<nd> q2;
void bfs(int X,int Y){
	vis[X][Y] = tim;
	q2.push(nd{X,Y});
	while(q2.size()){
		int x=q2.front().x, y=q2.front().y;
		q2.pop();
		for(int i=0;i<4;i++){
			int xx=x+dx[i],yy=y+dy[i];
			if(xx>R || yy>C || xx<1 || yy<1) continue;
			if(vis[xx][yy] == tim) continue;
			if(g[xx][yy] != '.') continue;
			if(waste(nd2{lay,n,n},f[xx][yy])) continue;
			if(f[xx][yy].lay != lay) q[now].push(nd{xx,yy});
			vis[xx][yy] = tim;
			f[xx][yy] = nd2{lay,n,n};
			q2.push(nd{xx,yy});
		}
		if(f[x][y].lay==lay && (f[x][y].r==n || f[x][y].c==n)) continue;
		for(int i=0;i<4;i++){
			int xx=x+dx[i],yy=y+dy[i];
			int rr=f[x][y].r+(dx[i]!=0), cc=f[x][y].c+(dy[i]!=0);
			if(f[x][y].lay != lay) rr=cc=1;
			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(f[xx][yy].lay != lay) q[now].push(nd{xx,yy});
			vis[xx][yy] = tim;
			f[xx][yy] = nd2{lay,rr,cc};
			q2.push(nd{xx,yy});
		}
	}
}
int main(){
//	freopen("data.in","r",stdin);
	scanf("%d%d%d",&R,&C,&n);
	scanf("%d%d%d%d",&sx,&sy,&ex,&ey);
	for(int i=1;i<=R;i++){
		f[i].resize(C+1);
		vis[i].resize(C+1);
		cin>>g[i]; g[i]=' '+g[i];
		for(int j=1;j<=C;j++)
			f[i][j].lay = inf;
	}
	dfs0(sx,sy);
	if(f[ex][ey].lay!=inf) {printf("0\n"); return 0;}
	for(lay=2;;lay++){
		// cout<<lay<<endl;
		// for(int i=1;i<=R;i++){
		// 	for(int j=1;j<=C;j++){
		// 		if(f[i][j].lay==inf) printf("0 ");
		// 		else printf("%d ",f[i][j].lay);
		// 	}
		// 	puts("");
		// }
		swap(now,pre);
	//	cout<<q[pre].size()<<endl;
		while(q[pre].size()){
			int x=q[pre].front().x;
			int y=q[pre].front().y;
			q[pre].pop();
			tim++;
			bfs(x,y);
		}
		if(f[ex][ey].lay!=inf){printf("%d\n",lay-1); return 0;}
	}
	return 0;
}