#include <bits/stdc++.h>
using namespace std;
void solve(){
int r,c,n;
cin >> r >> c >> n;
pair < int , int > s,g;
cin >> s.first >> s.second >> g.first >> g.second;
s.first--;s.second--;g.first--;g.second--;
int grid[r][c];
set < int > hor[r] , ver[c];
for(int i = 0;i<r;i++){//1 = # , 0 = .
string str;cin >> str;
for(int j = 0;j<c;j++){
grid[i][j] = str[j] == '#';
if(i != s.first or j != s.second){
ver[j].insert(i);
hor[i].insert(j);
}
}
}
priority_queue < pair < int , pair < int , int > > > bfs;//{dist,{x,y}}
bfs.push({0,s});
int vis[r][c];
memset(vis , 0 , sizeof(vis));
while(bfs.size()){
pair < int , int > p = bfs.top().second;
int dist = -bfs.top().first;
bfs.pop();
if(vis[p.first][p.second])continue;
//cout << "bfs : " << p.first << " " << p.second << " " << dist << endl;
vis[p.first][p.second] = 1;
if(p == g){
cout << dist << '\n';
return;
}
//spread
if((p.first+n) < r){// ({n,-n} , {n,n})
auto lb = hor[p.first + n].upper_bound(p.second - n);
auto ub = hor[p.first + n].lower_bound(p.second + n);
if(lb != hor[p.first + n].end() and ub != hor[p.first + n].begin()){
vector < int > willdel;
for(auto it = lb;it != ub;++it){
willdel.push_back(*it);
}
for(auto itr : willdel){
bfs.push({-dist-1,{p.first + n , itr}});
hor[p.first + n].extract(itr);
ver[itr].extract(p.first + n);
}
}
}
if((p.first - n) >= 0){// ({-n,-n} , {-n,n})
auto lb = hor[p.first - n].upper_bound(p.second - n);
auto ub = hor[p.first - n].lower_bound(p.second + n);
if(lb != hor[p.first - n].end() and ub != hor[p.first - n].begin()){
vector < int > willdel;
for(auto it = lb;it != ub;++it){
willdel.push_back(*it);
}
for(auto itr : willdel){
bfs.push({-dist-1,{p.first - n , itr}});
hor[p.first - n].extract(itr);
ver[itr].extract(p.first - n);
}
}
}
if((p.second + n) < c){// ({-n,n} , {n,n})
auto lb = ver[p.second + n].upper_bound(p.first - n);
auto ub = ver[p.second + n].lower_bound(p.first + n);
if(lb != ver[p.second + n].end() and ub != ver[p.second + n].begin()){
vector < int > willdel;
for(auto it = lb;it != ub;++it){
willdel.push_back(*it);
}
for(auto itr : willdel){
bfs.push({-dist-1,{itr , p.second + n,}});
ver[p.second + n].extract(itr);
hor[itr].extract(p.second + n);
}
}
}
if((p.second - n) >= 0){// ({-n,-n} , {n,-n})
auto lb = ver[p.second - n].upper_bound(p.first - n);
auto ub = ver[p.second - n].lower_bound(p.first + n);
if(lb != ver[p.second - n].end() and ub != ver[p.second - n].begin()){
vector < int > willdel;
for(auto it = lb;it != ub;++it){
willdel.push_back(*it);
}
for(auto itr : willdel){
bfs.push({-dist-1,{itr , p.second - n,}});
ver[p.second - n].extract(itr);
hor[itr].extract(p.second - n);
}
}
}
if(p.first != 0 and grid[p.first-1][p.second] == 0)bfs.push({-dist,{p.first-1,p.second}});
if(p.second != 0 and grid[p.first][p.second-1] == 0)bfs.push({-dist,{p.first,p.second-1}});
if(p.first != (r-1) and grid[p.first+1][p.second] == 0)bfs.push({-dist,{p.first+1,p.second}});
if(p.second != (c-1) and grid[p.first][p.second+1] == 0)bfs.push({-dist,{p.first,p.second+1}});
if((abs(g.first - p.first) <= n and abs(g.second - p.second) <= (n-1)) or (abs(g.first - p.first) <= (n-1) and abs(g.second - p.second) <= n)){
bfs.push({-dist-1,g});
}
}
cout << -1 << '\n';
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int testcase = 1;//cin >> testcase;
while(testcase--)solve();
}
