#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int R, C, N;
cin >> R >> C >> N;
int sr, sc, gr, gc;
cin >> sr >> sc;
cin >> gr >> gc;
--sr; --sc; --gr; --gc;
vector<string> a(R);
for (int i = 0; i < R; i++) cin >> a[i];
auto id = [&](int r, int c) {
return r * C + c;
};
int S = id(sr, sc);
int G = id(gr, gc);
vector<unsigned char> reached(R * C, 0);
vector<unsigned char> in_border(R * C, 0);
vector<int> active;
active.push_back(S);
reached[S] = 1;
int ans = 0;
while (true) {
queue<int> q;
vector<int> touched;
touched.reserve(active.size());
for (int v : active) q.push(v);
while (!q.empty()) {
int v = q.front();
q.pop();
touched.push_back(v);
if (v == G) {
cout << ans << '\n';
return 0;
}
int r = v / C;
int c = v % C;
if (r > 0) {
int u = v - C;
if (!reached[u] && a[r - 1][c] == '.') {
reached[u] = 1;
q.push(u);
}
}
if (r + 1 < R) {
int u = v + C;
if (!reached[u] && a[r + 1][c] == '.') {
reached[u] = 1;
q.push(u);
}
}
if (c > 0) {
int u = v - 1;
if (!reached[u] && a[r][c - 1] == '.') {
reached[u] = 1;
q.push(u);
}
}
if (c + 1 < C) {
int u = v + 1;
if (!reached[u] && a[r][c + 1] == '.') {
reached[u] = 1;
q.push(u);
}
}
}
vector<int> border;
border.reserve(touched.size() * 2);
for (int v : touched) {
int r = v / C;
int c = v % C;
if (r > 0) {
int u = v - C;
if (!reached[u] && a[r - 1][c] == '#' && !in_border[u]) {
in_border[u] = 1;
border.push_back(u);
}
}
if (r + 1 < R) {
int u = v + C;
if (!reached[u] && a[r + 1][c] == '#' && !in_border[u]) {
in_border[u] = 1;
border.push_back(u);
}
}
if (c > 0) {
int u = v - 1;
if (!reached[u] && a[r][c - 1] == '#' && !in_border[u]) {
in_border[u] = 1;
border.push_back(u);
}
}
if (c + 1 < C) {
int u = v + 1;
if (!reached[u] && a[r][c + 1] == '#' && !in_border[u]) {
in_border[u] = 1;
border.push_back(u);
}
}
}
for (int v : border) in_border[v] = 0;
if (border.empty()) {
cout << -1 << '\n';
return 0;
}
vector<vector<pair<int,int>>> segs(R);
for (int v : border) {
int r = v / C;
int c = v % C;
int r1 = max(0, r - (N - 1));
int r2 = min(R - 1, r + (N - 1));
int c1 = max(0, c - (N - 1));
int c2 = min(C - 1, c + (N - 1));
for (int rr = r1; rr <= r2; rr++) {
segs[rr].push_back({c1, c2});
}
}
vector<int> next_active;
for (int r = 0; r < R; r++) {
if (segs[r].empty()) continue;
sort(segs[r].begin(), segs[r].end());
int L = segs[r][0].first;
int Rr = segs[r][0].second;
auto process_segment = [&](int l, int rr) {
for (int c = l; c <= rr; c++) {
int v = id(r, c);
if (reached[v]) continue;
reached[v] = 1;
next_active.push_back(v);
}
};
for (int i = 1; i < (int)segs[r].size(); i++) {
if (segs[r][i].first <= Rr + 1) {
Rr = max(Rr, segs[r][i].second);
} else {
process_segment(L, Rr);
L = segs[r][i].first;
Rr = segs[r][i].second;
}
}
process_segment(L, Rr);
}
if (next_active.empty()) {
cout << -1 << '\n';
return 0;
}
active.swap(next_active);
ans++;
}
return 0;
}
