#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
using namespace std;
inline int read()
{
	char c=getchar();int x=0;bool f=0;
	for(;!isdigit(c);c=getchar())f^=!(c^45);
	for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
	if(f)x=-x;return x;
}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 6000005
#define inf 0x3f3f3f3f

int n,m,k;
string mp[maxn];


int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

int P(int o,int x,int y){
	return o*n*m+x*m+y;
}
int dis[maxn*5];
bool vis[maxn*5];

int q[maxn*10];
int hd=maxn*5,tl=maxn*5-1;

int ddx[5][2]={{0,0},{1,0},{1,0},{-1,0},{-1,0}};
int ddy[5][2]={{0,0},{0,1},{0,-1},{0,-1},{0,1}}; 

pii B(int x,int y){
	return mkp(x/k,y/k);
}

int L(int x){
	return x*k;
}
int R(int x){
	return (x+1)*k-1;
}

void go(int x,int d){
	if(dis[x]>d){
		dis[x]=d;
		q[--hd]=x;
	}
}

inline void go(int o,int x,int y,int d){
	x=max(x,0),y=max(y,0);
	x=min(x,n-1),y=min(y,m-1);
	int u=P(o,x,y);
	if(dis[u]>d){
		dis[u]=d;
		q[++tl]=u;
	}
}

void work()
{
	ios::sync_with_stdio(0),cin.tie(0); 
	cin>>n>>m>>k;
	memset(dis,63,sizeof dis);
	int sx,sy,tx,ty;
	cin>>sx>>sy>>tx>>ty;
	For(i,0,n-1)cin>>mp[i];
	--sx,--sy,--tx,--ty;
	q[++tl]=P(0,sx,sy); dis[P(0,sx,sy)]=0; 
	while(hd<=tl){
		int U=q[hd++];
		int o=(U/(n*m)),x=((U%(n*m))/m),y=(U%m);
		int d=dis[U];
		if(vis[U])continue;
		vis[U]=1;
	//	cout<<o<<" "<<x<<" "<<y<<" "<<d<<"\n";
		if(o==0){
			For(i,0,4){
				int xx=x+dx[i],yy=y+dy[i];
				if(xx>=0 && yy>=0 && xx<n && yy<m && mp[xx][yy]!='#')
					go(P(0,xx,yy),d);
			}
			int bx=x/k,by=y/k;
			int rbx=R(bx),rby=R(by);
			
			go(3,rbx,rby,d+1);
			
			go(2,x-k,rby,d+1);
			go(4,rbx,y-k,d+1);
			go(3,rbx,y+k,d+1);
			go(3,x+k,rby,d+1);
			
			go(1,x-k+1,y-k,d+1);
			go(1,x-k+1,y-k+1,d+1);
			go(2,x-k,y+k-1,d+1);
			go(2,x-k+1,y+k,d+1);
			go(3,x+k-1,y+k,d+1);
			go(3,x+k,y+k-1,d+1);
			go(4,x+k,y-k+1,d+1);
			go(4,x+k-1,y-k,d+1);
			
		}else{
			For(i,0,1){
				int xx=x+ddx[o][i],yy=y+ddy[o][i];
				if(xx>=0 && yy>=0 && xx<n && yy<m && (xx/k)==(x/k) && (yy/k)==(y/k))
					go(P(o,xx,yy),d);
			}
			go(P(0,x,y),d);
		}
	}
	cout<<dis[P(0,tx,ty)];
}

signed main()
{
	work();
	return 0;
}
/*

6 6 1
1 6
6 1
..#.#.
##.###
####.#
...###
##.##.
.#.###


6 7 2
6 4
3 1
..#.#.#
##.##..
.######
#..#.#.
.######
..#.##.
*/