#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int r, c, N;
cin >> r >> c >> N;
int sti, stj, eni, enj;
cin >> sti >> stj >> eni >> enj;
sti -= 1;
stj -= 1;
eni -= 1;
enj -= 1;
N -= 1;
vector<vector<char>> a(r, vector<char>(c));
for (int i =0 ; i < r; ++i) {
for (int j =0 ; j < c; ++j) {
cin >> a[i][j];
}
}
vector<vector<array<int, 3>>> dist(r, vector<array<int, 3>>(c, {r * c + 1, -1, -1}));
vector<array<int, 2>> q1, q2;
auto push = [&](vector<array<int, 2>>& q, int i, int j, int x, int y, int z) -> void {
if (i < 0 || j < 0 || i >= r || j >= c) return;
if (dist[i][j][0] <= x) return;
dist[i][j] = {x, y, z};
q.push_back({i, j});
};
auto push2 = [&](int i, int j, int x) -> void {
if (i < 0 || j < 0 || i >= r || j >= c) return;
if (a[i][j] == '#') push(q2, i, j, x + 1, N, N);
else push(q1, i, j, x, 0, 0);
};
push(q1, sti, stj, 0, 0, 0);
while (q1.size()) {
for (int it = 0; it < (int)q1.size(); ++it) {
auto [i, j] = q1[it];
auto [x, y, z] = dist[i][j];
if (y > 0) {
push(q1, i - 1, j, x, y - 1, z);
push(q1, i + 1, j, x, y - 1, z);
}
}
for (int it = 0; it < (int)q1.size(); ++it) {
auto [i, j] = q1[it];
auto [x, y, z] = dist[i][j];
if (z > 0) {
push(q1, i, j - 1, x, y, z - 1);
push(q1, i, j + 1, x, y, z - 1);
}
}
for (int it = 0; it < (int)q1.size(); ++it) {
auto [i, j] = q1[it];
//~ cout << i << " " << j << "\n";
auto [x, y, z] = dist[i][j];
push2(i - 1, j, x);
push2(i + 1, j, x);
push2(i, j - 1, x);
push2(i, j + 1, x);
}
swap(q1, q2);
q2.clear();
}
cout << dist[eni][enj][0] << "\n";
}
