#include <bits/stdc++.h>
#define f first
#define s second
#define inf 10000000
using namespace std;
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<ii,ii> iii;
typedef pair<ii,iii> iiii;
priority_queue <iiii> q; // distancia, distancia pro ponto base da carimbada, x e y do ponto base da carimbada, i, j
int difx[4] = {0, 1, 0, -1};
int dify[4] = {1, 0, -1, 0};
int r, c, n;
vvi dist;
vvi m;
void bfs(ii ini){
int i, a, b;
q.push({{0, 0}, {{-1, -1}, {ini.f, ini.s}}});
iiii next;
while(!q.empty()){
next = q.top();
q.pop();
if(dist[next.s.s.f][next.s.s.s]<=-next.f.f) continue;
dist[next.s.s.f][next.s.s.s]=-next.f.f;
for(i=0;i<4;i++){
a = next.s.s.f+difx[i];
b = next.s.s.s+dify[i];
if(a<0 || a==r || b<0 || b==c) continue;
if(dist[a][b]==inf){
if(m[a][b]){
if(next.s.f.s==-1 || abs(a-next.s.f.f)==n || abs(b-next.s.f.s)==n)
q.push({{next.f.f, 0}, {{-1, -1}, {a, b}}});
else
q.push({{next.f.f, next.f.s-1}, {next.s.f, {a, b}}});
}
else{
if(next.s.f.s==-1 || abs(a-next.s.f.f)==n || abs(b-next.s.f.s)==n)
q.push({{next.f.f-1, 0}, {{a, b}, {a, b}}});
else
q.push({{next.f.f, next.f.s-1}, {next.s.f, {a, b}}});
}
}
}
}
}
int main (){
int i, j;
char a;
ii fim, ini;
cin >> r >> c >> n;
m = vvi(r, vi(c, 0));
dist = vvi(r, vi(c, inf));
cin >> ini.f >> ini.s;
ini.f--;ini.s--;
cin >> fim.f >> fim.s;
fim.s--;fim.f--;
for(i=0;i<r;i++){
for(j=0;j<c;j++){
cin >> a;
if(a=='.') m[i][j] = 1; // # = 0 (preto) e . = 1 (branco)
dist[i][j] = inf;
}
}
bfs(ini);
cout << dist[fim.f][fim.s] << endl;
return 0;
}
