#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 inside = [&](int r, int c) {
return 0 <= r && r < R && 0 <= c && c < C;
};
auto id = [&](int r, int c) {
return r * C + c;
};
int V = R * C;
int S = id(sr, sc);
int G = id(gr, gc);
vector<unsigned char> reached(V, 0), inBorder(V, 0);
vector<int> active = {S};
reached[S] = 1;
int ans = 0;
while (true) {
if (reached[G]) {
cout << ans << '\n';
return 0;
}
queue<int> q;
vector<int> newly;
newly.reserve(active.size());
for (int v : active) q.push(v);
while (!q.empty()) {
int v = q.front();
q.pop();
int r = v / C;
int c = v % C;
int dr[4] = {-1, 1, 0, 0};
int dc[4] = {0, 0, -1, 1};
for (int k = 0; k < 4; k++) {
int nr = r + dr[k], nc = c + dc[k];
if (!inside(nr, nc)) continue;
int u = id(nr, nc);
if (reached[u]) continue;
if (a[nr][nc] != '.') continue;
reached[u] = 1;
newly.push_back(u);
q.push(u);
}
}
for (int v : active) newly.push_back(v);
if (reached[G]) {
cout << ans << '\n';
return 0;
}
vector<int> border;
border.reserve(newly.size() * 2);
for (int v : newly) {
int r = v / C;
int c = v % C;
int dr[4] = {-1, 1, 0, 0};
int dc[4] = {0, 0, -1, 1};
for (int k = 0; k < 4; k++) {
int nr = r + dr[k], nc = c + dc[k];
if (!inside(nr, nc)) continue;
int u = id(nr, nc);
if (reached[u]) continue;
if (a[nr][nc] != '#') continue;
if (inBorder[u]) continue;
inBorder[u] = 1;
border.push_back(u);
}
}
if (border.empty()) {
cout << -1 << '\n';
return 0;
}
vector<int> diff((R + 1) * (C + 1), 0);
auto add_rect = [&](int r1, int c1, int r2, int c2) {
if (r1 > r2 || c1 > c2) return;
diff[r1 * (C + 1) + c1] += 1;
diff[r1 * (C + 1) + (c2 + 1)] -= 1;
diff[(r2 + 1) * (C + 1) + c1] -= 1;
diff[(r2 + 1) * (C + 1) + (c2 + 1)] += 1;
};
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));
add_rect(r1, c1, r2, c2);
}
for (int r = 0; r <= R; r++) {
for (int c = 1; c <= C; c++) {
diff[r * (C + 1) + c] += diff[r * (C + 1) + (c - 1)];
}
}
for (int c = 0; c <= C; c++) {
for (int r = 1; r <= R; r++) {
diff[r * (C + 1) + c] += diff[(r - 1) * (C + 1) + c];
}
}
vector<int> nextActive;
nextActive.reserve(border.size());
for (int r = 0; r < R; r++) {
for (int c = 0; c < C; c++) {
if (diff[r * (C + 1) + c] <= 0) continue;
int v = id(r, c);
if (reached[v]) continue;
nextActive.push_back(v);
}
}
for (int v : border) inBorder[v] = 0;
if (nextActive.empty()) {
cout << -1 << '\n';
return 0;
}
for (int v : nextActive) reached[v] = 1;
active.swap(nextActive);
ans++;
}
}
