#include <bits/stdc++.h>
using namespace std;
const int N=6e6+5,inf=0x3f3f3f3f;
int dx[] = {-1,1,0,0};
int dy[] = {0,0,-1,1};
int R,C,n;
int sx,sy,ex,ey;
string g[N];
vector<int> vis[N];
struct nd{int x,y,lay,r,c;};
queue<nd> q[2];
int now=0,nxt=1;
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];
		vis[i].resize(C+1);
		for(int j=1;j<=C;j++)
			vis[i][j] = inf;
	}
	q[now].push(nd{sx,sy,0,n,n});
	vis[sx][sy] = 0;
	while(q[now].size()){
		nd f=q[now].front(); q[now].pop();
//		printf("%d %d %d %d %d\n",f.x,f.y,f.lay,f.r,f.c);
		if(f.x==ex && f.y==ey) {printf("%d\n",f.lay); return 0;}
		for(int i=0;i<4;i++){
			int xx=f.x+dx[i],yy=f.y+dy[i];
			int rr=f.r+(i<2),cc=f.c+(i>1);
			if(xx>R || yy>C || xx<1 || yy<1 || vis[xx][yy]<=f.lay) continue;
			if(g[xx][yy] == '.'){
				q[now].push(nd{xx,yy,f.lay,rr,cc});
				vis[xx][yy] = f.lay;
			}
			else{
				if(rr>n || cc>n){
					q[nxt].push(nd{xx,yy,f.lay+1,1,1});
					vis[xx][yy] = f.lay+1;
				}
				else{
					q[now].push(nd{xx,yy,f.lay,rr,cc});
					vis[xx][yy] = f.lay;
				}
			}
		}
		if(!q[now].size()) swap(now,nxt);
	}
	return 0;
}