#include <bits/stdc++.h>

// #define int int64_t

const int kMaxT = 6e6 + 5, kMaxN = 3e3 + 5;
const int kD4[][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
const int kD8[][2] = {{1, 1}, {1, -1}, {-1, 1}, {-1, -1}, {0, 1}, {0, -1}, {1, 0}, {-1, 0}};

int n, m, k;
int sx, sy, tx, ty;
std::vector<int> G[kMaxT];
std::string s[kMaxN];

void dijkstra() {
  std::vector<std::vector<std::pair<int, int>>> dis(n + 1, std::vector<std::pair<int, int>>(m + 1));
  // std::deque<std::pair<int, int>> q;
  std::vector<std::vector<bool>> vis(n + 1, std::vector<bool>(m + 1));
  std::priority_queue<std::tuple<int, int, int, int>> q;
  for (int i = 1; i <= n; ++i)
    for (int j = 1; j <= m; ++j)
      dis[i][j] = {1e9, 1e9};
  // q.emplace_back(sx, sy);
  dis[sx][sy] = {0, k - 1};
  q.emplace(0, -(k - 1), sx, sy);
  for (; !q.empty();) {
    auto [d, w, x, y] = q.top();
    q.pop();
    if (vis[x][y]) continue;
    vis[x][y] = 1;
    for (auto [dx, dy] : kD4) {
      int tx = x + dx, ty = y + dy;
      if (tx < 1 || tx > n || ty < 1 || ty > m) continue;
      if (s[tx][ty] == '.') {
        std::pair<int, int> p = {dis[x][y].first, k - 1};
        if (dis[tx][ty] > p) {
          dis[tx][ty] = p;
          q.emplace(-p.first, -p.second, tx, ty);
        }
      }
      std::pair<int, int> p = {dis[x][y].first + 1, 0};
      if (dis[tx][ty] > p) {
        dis[tx][ty] = p;
        q.emplace(-p.first, -p.second, tx, ty);
      }
    }
    if (dis[x][y].second < k - 1) {
      for (auto [dx, dy] : kD8) {
        int tx = x + dx, ty = y + dy;
        if (tx < 1 || tx > n || ty < 1 || ty > m) continue;
        std::pair<int, int> p = {dis[x][y].first, dis[x][y].second + 1};
        if (dis[tx][ty] > p) {
          dis[tx][ty] = p;
          q.emplace(-p.first, -p.second, tx, ty);
        }
      }
    }
  }
  std::cout << dis[tx][ty].first << '\n';
}

void dickdreamer() {
  std::cin >> n >> m >> k >> sx >> sy >> tx >> ty;
  for (int i = 1; i <= n; ++i) {
    std::cin >> s[i];
    s[i] = " " + s[i];
  }
  dijkstra();
}

int32_t main() {
#ifdef ORZXKR
  freopen("in.txt", "r", stdin);
  freopen("out.txt", "w", stdout);
#endif
  std::ios::sync_with_stdio(0), std::cin.tie(0), std::cout.tie(0);
  int T = 1;
  // std::cin >> T;
  while (T--) dickdreamer();
  // std::cerr << 1.0 * clock() / CLOCKS_PER_SEC << "s\n";
  return 0;
}