#include<bits/stdc++.h>
using namespace std;
int n,m,k,sx,sy,xx,yy;
struct node{int x,y,val,res;};
deque<node>q;
vector<string>a;
vector<vector<bool>>vis;
int dx4[4]={0,0,1,-1};
int dy4[4]={1,-1,0,0};
int dx8[8]={1,1,1,-1,-1,-1,0,0};
int dy8[8]={0,-1,1,0,1,-1,1,-1};
int main(){
	int x,y,val,res,tx,ty;
	scanf("%d%d%d%d%d%d%d",&n,&m,&k,&sx,&sy,&xx,&yy);
	a.resize(n+1);vis.resize(n+1);
	for(int i=0;i<=n;++i)vis[i].resize(m+1);
	for(int i=1;i<=n;++i)cin>>a[i],a[i]='~'+a[i];
	q.push_back({sx,sy,0,0});
	while(!q.empty()){
		auto u=q.front();q.pop_front();
		x=u.x;y=u.y;val=u.val;res=u.res;
		if(vis[x][y])continue;vis[x][y]=1;
		if(x==xx&&y==yy)return printf("%d",val),0;
		if(res--){
			for(int i=0;i<8;++i){
				tx=x+dx8[i];ty=y+dy8[i];
				if(tx<1||ty<1||tx>n||ty>m)continue;
				q.push_front({tx,ty,val,res});
			}
		}else{
			for(int i=0;i<4;++i){
				tx=x+dx4[i];ty=y+dy4[i];
				if(tx<1||ty<1||tx>n||ty>m)continue;
				if(a[tx][ty]=='.')q.push_front({tx,ty,val,0});
				else q.push_back({tx,ty,val+1,k-1});
			}
		}
	}
}