#include "bits/stdc++.h"
#define int long long
#define all(v) v.begin() , v.end()
#define sz(a) (int)a.size()
using namespace std;
int n,m,k,a,b,c,d;
vector<vector<int>> v,dist,vis,pot;
const int INF = 1e9;
bool is_valid(int x,int y){
return (x>=1 && x<=n && y>=1 && y<=m && !v[x][y] && !vis[x][y]);
}
bool _Valid(int x,int y){
return (x>=1 && x<=n && y>=1 && y<=m && !vis[x][y]);
}
vector<array<int,2>> Extend(queue<array<int,2>> q){
vector<array<int,2>> New;
while(!q.empty()){
int A=q.front()[0],B=q.front()[1];
q.pop();
for(int dx=-1;dx<=1;dx++)
for(int dy=-1;dy<=1;dy++)
if(is_valid(A+dx,B+dy) && abs(dx)+abs(dy)==1){
q.push({A+dx,B+dy});
New.push_back({A+dx,B+dy});
vis[A+dx][B+dy]=1;
dist[A+dx][B+dy]=dist[A][B];
}
}
return New;
}
vector<array<int,2>> Update(queue<array<int,2>> q){
vector<array<int,2>> New;
while(!q.empty()){
int A=q.front()[0],B=q.front()[1];
q.pop();
for(int dx=-1;dx<=1;dx++)
for(int dy=-1;dy<=1;dy++){
if(!_Valid(A+dx,B+dy)) continue;
if(pot[A][B]==k) continue;
if(pot[A][B]==0 && abs(dx)+abs(dy)==1){
q.push({A+dx,B+dy});
New.push_back({A+dx,B+dy});
vis[A+dx][B+dy]=1;
dist[A+dx][B+dy]=dist[A][B]+1;
pot[A+dx][B+dy]=pot[A][B]+1;
}
if(pot[A][B]>0){
q.push({A+dx,B+dy});
New.push_back({A+dx,B+dy});
vis[A+dx][B+dy]=1;
dist[A+dx][B+dy]=dist[A][B];
pot[A+dx][B+dy]=pot[A][B]+1;
}
}
}
return New;
}
void _(){
cin >> n >> m >> k;
cin >> a >> b >> c >> d;
dist.assign(n+5,vector<int>(m+5,INF));
v.assign(n+5,vector<int>(m+5,0));
pot.assign(n+5,vector<int>(m+5,0));
vis.assign(n+5,vector<int>(m+5,0));
for(int i=1;i<=n;i++){
string s;cin >> s;
for(int j=1;j<=m;j++){
if(s[j-1]=='.') v[i][j]=0;
else v[i][j]=1;
}
}
pot[a][b]=dist[a][b]=0;
vis[a][b]=1;
queue<array<int,2>> q;
q.push({a,b});
while(dist[c][d]==INF){
vector<array<int,2>> round;
queue<array<int,2>> qq=q;
vector<array<int,2>> cur=Extend(qq);
for(array<int,2> x:cur){
round.push_back(x);
q.push(x);
}
qq=q;
vector<array<int,2>> Swarm=Update(qq);
for(array<int,2> x:Swarm) round.push_back(x);
for(array<int,2> x:round) pot[x[0]][x[1]]=0;
while(!q.empty()) q.pop();
for(array<int,2> x:round) q.push(x);
}
cout << dist[c][d] << '\n';
}
int32_t main(){
cin.tie(0); ios::sync_with_stdio(0);
int tc=1;//cin >> tc;
while(tc--) _();
return 0;
}
