#include<bits/stdc++.h>
#define taskname "C"
using namespace std;
template<class T>bool minimize(T& a, T b){
if(a > b){
a = b;
return true;
}
return false;
}
const int dirx[8] = {-1, 0, 1, 0, -1, -1, 1, 1}, diry[8] = {0, 1, 0, -1, -1, 1, 1, -1};
const int INF = 1e9;
int k, n, m, sx, sy, tx, ty;
vector<vector<char>>a;
namespace sub1{
void solve(){
vector<vector<int>>f(n + 1, vector<int>(m + 1, -1));
f[sx][sy] = 0;
deque<pair<int, int>>dq;
dq.push_back(make_pair(sx, sy));
while(!dq.empty()){
tie(sx, sy) = dq.front();
dq.pop_front();
for(int i = 0; i < 4; i++){
int tx = sx + dirx[i], ty = sy + diry[i];
if(min(tx, ty) > 0 && tx <= n && ty <= m && f[tx][ty] == -1){
if(a[tx][ty] == '#'){
f[tx][ty] = f[sx][sy] + 1;
dq.push_back(make_pair(tx, ty));
}
else{
f[tx][ty] = f[sx][sy];
dq.push_front(make_pair(tx, ty));
}
}
}
}
cout << f[tx][ty];
}
}
namespace sub2{
struct Data{
int x, y, w;
Data(){}
Data(int _x, int _y, int _w) : x(_x), y(_y), w(_w) {}
friend bool operator <(const Data a, const Data b){
return a.w > b.w;
}
};
void solve(){
vector<vector<int>>f(n + 1, vector<int>(m + 1, INF)), dp(n + 1, vector<int>(m + 1, INF));
for(int i = dp[0][0] = 0; i <= n; i++){
for(int j = int(i == 0); j <= m; j++){
dp[i][j] = min(dp[max(0, i - k)][max(0, j - k + 1)], dp[max(0, i - k + 1)][max(0, j - k)]) + 1;
}
}
priority_queue<Data>pq;
pq.push(Data(sx, sy, f[sx][sy] = 0));
int sw;
while(!pq.empty()){
Data cur = pq.top();
pq.pop();
if((sw = cur.w) == f[sx = cur.x][sy = cur.y]){
for(int i = 0; i < 4; i++){
int tx = sx + dirx[i], ty = sy + diry[i];
if(min(tx, ty) > 0 && tx <= n && ty <= m && a[tx][ty] == '.' && minimize(f[tx][ty], sw)){
pq.push(Data(tx, ty, sw));
}
}
for(int tx = 1; tx <= n; tx++){
for(int ty = 1; ty <= m; ty++){
if(minimize(f[tx][ty], sw + dp[abs(tx - sx)][abs(ty - sy)])){
pq.push(Data(tx, ty, f[tx][ty]));
}
}
}
}
}
cout << f[tx][ty];
}
}
namespace sub45{
void solve(){
vector<set<int>>cand(n + 1);
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
if(a[i][j] == '#'){
cand[i].insert(j);
}
}
}
vector<pair<int, int>>p, np;
function<void(int, int)>dfs;
dfs = [&] (int x, int y){
if(x < 1 || x > n || y < 1 || y > m || a[x][y] == '#'){
return;
}
np.push_back(make_pair(x, y));
a[x][y] = '#';
for(int i = 0; i < 4; i++){
dfs(x + dirx[i], y + diry[i]);
}
};
dfs(sx, sy);
swap(p, np);
for(int iter = 0; true; iter++){
if(a[tx][ty] == '#'){
cout << iter;
break;
}
np.clear();
for(auto& [x, y] : p){
for(int i = max(1, x - k); i <= min(n, x + k); i++){
int left_bound = y - k + int(abs(i - x) == k), right_bound = y + k - int(abs(i - x) == k);
for(auto it = cand[i].lower_bound(left_bound); it != cand[i].end() && *it <= right_bound; it++){
a[i][*it] = '.';
dfs(i, *it);
}
cand[i].erase(cand[i].lower_bound(left_bound), cand[i].upper_bound(right_bound));
}
}
swap(p, np);
}
}
}
namespace sub3678{
struct Data{
int x, y, w, r;
Data(){}
Data(int _x, int _y, int _w, int _r) : x(_x), y(_y), w(_w), r(_r) {}
};
void solve(){
vector<vector<bool>>vis(n + 1, vector<bool>(m + 1, false));
deque<Data>dq;
dq.push_back(Data(sx, sy, 0, 0));
while(!dq.empty()){
auto [sx, sy, sw, sr] = dq.front();
dq.pop_front();
if(sx == tx && sy == ty){
return void(cout << sw);
}
if(!vis[sx][sy]){
vis[sx][sy] = true;
if(sr-- > 0){
for(int i = 0; i < 8; i++){
int tx = sx + dirx[i], ty = sy + diry[i];
if(min(tx, ty) > 0 && tx <= n && ty <= m){
dq.push_back(Data(tx, ty, sw, sr));
}
}
}
else{
for(int i = 0; i < 4; i++){
int tx = sx + dirx[i], ty = sy + diry[i];
if(min(tx, ty) > 0 && tx <= n && ty <= m){
if(a[tx][ty] == '.'){
dq.push_front(Data(tx, ty, sw, 0));
}
else{
dq.push_back(Data(tx, ty, sw + 1, k - 1));
}
}
}
}
}
}
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
if(fopen(taskname".inp", "r")){
freopen(taskname".inp", "r", stdin);
}
cin >> n >> m >> k >> sx >> sy >> tx >> ty;
a.assign(n + 1, vector<char>(m + 1));
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
cin >> a[i][j];
}
}
if(k == 1){
sub1::solve();
}
else if(n * m <= 1000){
sub2::solve();
}
else if(n * m <= 150000){
sub45::solve();
}
else{
sub3678::solve();
}
}
