#include <bits/stdc++.h>
using namespace std;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int R, C, N;
cin >> R >> C >> N;
int Sr, Sc, Gr, Gc;
cin >> Sr >> Sc >> Gr >> Gc;
Sr--; Sc--; Gr--; Gc--; // Convert to 0-indexed
vector<string> grid(R);
for (int i = 0; i < R; i++) {
cin >> grid[i];
}
// Helper function to find all reachable cells from given starts
auto bfsReachable = [&](const vector<pair<int, int>>& starts, vector<vector<bool>>& reachable) {
queue<pair<int, int>> q;
for (auto [x, y] : starts) {
if (!reachable[x][y]) {
reachable[x][y] = true;
q.push({x, y});
}
}
int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, -1, 1};
while (!q.empty()) {
auto [x, y] = q.front();
q.pop();
for (int d = 0; d < 4; d++) {
int nx = x + dx[d];
int ny = y + dy[d];
if (nx >= 0 && nx < R && ny >= 0 && ny < C &&
!reachable[nx][ny] && grid[nx][ny] == '.') {
reachable[nx][ny] = true;
q.push({nx, ny});
}
}
}
};
// Find initially reachable cells (0 operations)
vector<vector<bool>> reachable(R, vector<bool>(C, false));
bfsReachable({{Sr, Sc}}, reachable);
if (reachable[Gr][Gc]) {
cout << 0 << endl;
return 0;
}
// Level-by-level BFS on number of operations
for (int ops = 1; ops <= 50; ops++) {
vector<pair<int, int>> newStarts;
vector<vector<bool>> used(R - N + 1, vector<bool>(C - N + 1, false));
// Find all useful stamp positions for this level
for (int a = 0; a <= R - N; a++) {
for (int b = 0; b <= C - N; b++) {
if (used[a][b]) continue;
// Check if this stamp overlaps with currently reachable cells
bool canUse = false;
for (int i = a; i < a + N && !canUse; i++) {
for (int j = b; j < b + N && !canUse; j++) {
if (reachable[i][j]) {
canUse = true;
}
}
}
if (canUse) {
used[a][b] = true;
// Add all cells in this stamp as new starting points
for (int i = a; i < a + N; i++) {
for (int j = b; j < b + N; j++) {
if (!reachable[i][j]) {
newStarts.push_back({i, j});
}
}
}
}
}
}
// If no new starting points, we can't improve
if (newStarts.empty()) break;
// Expand reachability from new starting points
bfsReachable(newStarts, reachable);
if (reachable[Gr][Gc]) {
cout << ops << endl;
return 0;
}
}
cout << -1 << endl; // Should not happen for valid inputs
return 0;
}
