#include<bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int, int>
int R, C;
int N;
pii debut;
pii fin;
vector<vector<char>> maze;
vector<vector<int>> vis;
vector<vector<int>> oc;
vector<vector<int>> v_s;
pii delta[4] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
bool is_valid(pii pos){
if(pos.first>=R || pos.first< 0){
return false;
}
if(pos.second>=C || pos.second<0){
return false;
}
return true;
}
vector<pii> get_free(pii pos){
vector<pii> res;
for(auto d: delta){
pii c= {pos.first+d.first, pos.second+d.second};
if(is_valid(c) && maze[c.first][c.second] != '#'){
res.push_back(c);
}
}
return res;
}
void BFS(int cur){
deque<pair<pii, int>> dq;
for(int i = 0; i<R; i++){
for(int j = 0; j<C; j++){
if(vis[i][j]==cur+1){
dq.push_back({{i, j}, vis[i][j]});
}
}
}
while(dq.size()>0){
//display();
auto cur= dq.front();
dq.pop_front();
pii cur_pos =cur.first;
int dist = cur.second;
if(dist!= vis[cur_pos.first][cur_pos.second]){
continue;
}
for(auto e: get_free(cur_pos)){
if(vis[e.first][e.second] > dist){
vis[e.first][e.second] = dist;
dq.push_front({e, dist});
}
}
}
}
void spread(int cur){
for(int j = 0; j<C; j++){
for(int i = 0; i<R; i++){
v_s[i+1][j] = v_s[i][j] ;
if(vis[i][j]==cur){
v_s[i+1][j] ++;
}
}
}
for(int i = 0; i<R; i++){
int s= 0;
for(int j = 0; j<C; j++){
if(j == 0){
for(int k = 0; k<=N; k++){
//cout<<j+k<<endl;
s+= v_s[min(R, i+N+1)][j+k]-v_s[max(i-(N), 0LL)][j+k];
}
}
oc[i][j] = s ;
for(int di = -N; di<=N; di+=2*N){
for(int dj = -N; dj<=N; dj+=2*N){
if(is_valid({i+di, j+dj})){
oc[i][j]-=(v_s[i+di+1][j+dj]-v_s[i+di][j+dj]);
}
}
}
if(j-(N)>=0){
s-=v_s[min(R, i+N+1)][j-(N)]-v_s[max(i-(N), 0LL)][j-(N)];
}
if(j+N+1<C){
s+=v_s[min(R, i+N+1)][j+N+1]-v_s[max(i-(N), 0LL)][j+N+1];
}
}
}
for(int i = 0; i<R; i++){
for(int j = 0; j<C; j++){
if(oc[i][j]>0 && vis[i][j] == 1e9){
vis[i][j] = cur+1;
}
}
}
BFS(cur);
}
signed main(){
cin>>R>>C;
cin>>N;
maze.resize(R, vector<char> (C));
vis.resize(R, vector<int>(C, 1e9));
oc.resize(R, vector<int>(C));
v_s.resize(R+1, vector<int>(C, 0));
cin>>debut.first>>debut.second;
debut.first--;
debut.second--;
cin>>fin.first>>fin.second;
fin.first--;
fin.second--;
for(int i = 0; i<R; i++){
for(int j = 0; j<C; j++){
cin>>maze[i][j];
}
}
vis[debut.first][debut.second] = 0;
BFS(-1);
int c= 0;
while(vis[fin.first][fin.second] == 1e9 && c<=10){
spread(c);
c++;
}
cout<<vis[fin.first][fin.second]<<endl;
}
