#include <bits/stdc++.h>
using namespace std;
using idata = vector<int>;
using igrid = vector<idata>;
using bdata = vector<bool>;
using bgrid = vector<bdata>;
using point = pair<int, int>;
int N, M, B;
igrid visited;
bgrid isTransparent;
vector<point> adjacent (point source, bool diagonal) {
if (diagonal) {
return {
{ source.first - 1, source.second - 1 },
{ source.first + 1, source.second - 1 },
{ source.first - 1, source.second + 1 },
{ source.first + 1, source.second + 1 },
{ source.first, source.second - 1 },
{ source.first, source.second + 1 },
{ source.first - 1, source.second },
{ source.first + 1, source.second }
};
}
return {
{ source.first, source.second - 1 },
{ source.first, source.second + 1 },
{ source.first - 1, source.second },
{ source.first + 1, source.second }
};
}
int bfs (point source, point target) {
deque<point> bfs_queue;
visited[source.first][source.second] = 0;
bfs_queue.push_front(source);
while (bfs_queue.size() != 0) {
point current = bfs_queue.front();
bfs_queue.pop_front();
bool isDiagonal = visited[current.first][current.second] % B != 0;
for (point next : adjacent(current, isDiagonal)) {
if (next.first < 0 || next.first >= N) continue ;
if (next.second < 0 || next.second >= M) continue ;
if (visited[next.first][next.second] != -1) continue ;
bool plus = isDiagonal || (!isTransparent[next.first][next.second]);
if (plus) {
visited[next.first][next.second] = visited[current.first][current.second] + 1;
bfs_queue.push_back(next);
} else {
visited[next.first][next.second] = visited[current.first][current.second];
bfs_queue.push_front(next);
}
}
}
double a = visited[target.first][target.second];
double b = B;
return (int) ceil(a / b);
}
int main () {
cin >> N >> M >> B;
visited.resize(N, idata(M, - 1));
int sx, sy;
cin >> sx >> sy;
sx --; sy --;
int tx, ty;
cin >> tx >> ty;
tx --; ty --;
isTransparent.resize(N, bdata(M));
for (int i = 0; i < N; i ++) {
string buffer;
cin >> buffer;
for (int j = 0; j < M; j ++)
isTransparent[i][j] = buffer[j] == '.';
}
cout << bfs({ sx, sy }, { tx, ty }) << "\n";
}
