#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>
/*
#define push_back push
#define pop_front pop
#define push_front push
#define front top
priority_queue<node,vector<node>,greater<node>> dq;
void add(int lvl ,int r,int c,int d){
if(lvl>4||r<0||c<0||r>=R||c>=C)return;
//cout<<lvl<<','<<r<<' '<<c<<' '<<d<<endl;
if(dist[lvl][r][c] != -1&&dist[lvl][r][c]<=d)return;
dist[lvl][r][c] = d;
dq.push(node(lvl,r,c,d));
return;
}
*/
struct node{
int lvl,r,c,d;
node(){lvl = r = c = d = 0;}
node(int lv,int rr,int cc,int dd):lvl(lv),r(rr),c(cc),d(dd){}
bool operator<(node b)const{
return d<b.d;
}
bool operator>(node b)const{
return d>b.d;
}
};
int R,C,N;
vector<string> arr;
vector<vector<int>> dist[5];
pii s,e;
deque<node> dq;
pii dir[] = {{0,1},{0,-1},{1,0},{-1,0}};
pii dir2[] = {{1,1},{1,-1},{-1,-1},{-1,1}};
inline void add(int lvl,int r,int c,int d){
if(lvl>4||r<0||c<0||r>=R||c>=C)return;
//cout<<lvl<<','<<r<<' '<<c<<' '<<d<<endl;
if(dist[lvl][r][c] != -1&&dist[lvl][r][c]<=d)return;
dist[lvl][r][c] = d;
if(dq.empty()||dq.back().d<=d)dq.push_back(node(lvl,r,c,d));
else dq.push_front(node(lvl,r,c,d));
}
void add_center(int r,int c,int d){//extend radius of N square
for(int i = 0;i<4;i++){
int nr = r-dir2[i].fs*(N-1),nc = c-dir2[i].sc*(N-1);
nr = min(nr,R-1),nr = max(nr,0),nc = min(nc,C-1),nc = max(nc,0);
add(i,nr,nc,d);
}
return;
}
void BFS(pii s){
add(4,s.fs,s.sc,0);
dist[4][s.fs][s.sc] = 0;
while(!dq.empty()){
auto now = dq.front();
dq.pop_front();
if(dist[now.lvl][now.r][now.c] != now.d)continue;
//cout<<now.lvl<<','<<now.r<<' '<<now.c<<':'<<now.d<<endl;
if(now.lvl == 4){
add_center(now.r,now.c,now.d+1);
for(auto &d:dir){
int nr = d.fs+now.r,nc = d.sc+now.c;
//cout<<nr<<','<<nc<<endl;
if(nr>=0&&nc>=0&&nr<R&&nc<C){
add_center(nr,nc,now.d+1);
add(4,nr,nc,now.d+(arr[nr][nc] == '#'));
}
}
}
else{
add(4,now.r,now.c,now.d);
int nr = now.r+dir2[now.lvl].fs,nc = now.c+dir2[now.lvl].sc;
if(nr>=0&&nr<R&&now.r%(N*2-1) != 0)add(now.lvl,nr,now.c,now.d);
if(nc>=0&&nc<C&&now.c%(N*2-1) != 0)add(now.lvl,now.r,nc,now.d);
}
}
return;
}
main(){
ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin>>R>>C>>N;
arr = vector<string>(R);
dist[0] = dist[1] = dist[2] = dist[3] = dist[4] = vector<vector<int>>(R,vector<int>(C,-1));
cin>>s.fs>>s.sc>>e.fs>>e.sc;
s.fs--,s.sc--,e.fs--,e.sc--;
for(auto &i:arr)cin>>i;
BFS(s);
cout<<dist[4][e.fs][e.sc];
}
