#line 1 "/workspaces/compro/lib/template.hpp"


#line 1 "/workspaces/compro/lib/io/vector.hpp"
#include <iostream>
#include <vector>

#ifndef IO_VECTOR
#define IO_VECTOR

template <class T> std::ostream &operator<<(std::ostream &out, const std::vector<T> &v) {
  int size = v.size();
  for (int i = 0; i < size; i++) {
    std::cout << v[i];
    if (i != size - 1)
      std::cout << " ";
  }
  return out;
}

template <class T> std::istream &operator>>(std::istream &in, std::vector<T> &v) {
  for (auto &el : v) {
    std::cin >> el;
  }
  return in;
}

#endif
#line 4 "/workspaces/compro/lib/template.hpp"
#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define ALL(v) (v).begin(), (v).end()
#define coutd(n) cout << fixed << setprecision(n)
#define ll long long int
#define vl vector<ll>
#define vi vector<int>
#define MM << " " <<

using namespace std;

template <class T> void say(bool val, T yes, T no) { cout << (val ? yes : no) << "\n"; }

void say(bool val, string yes = "Yes", string no = "No") { say<string>(val, yes, no); }

template <class T> void chmin(T &a, T b) {
  if (a > b)
    a = b;
}

template <class T> void chmax(T &a, T b) {
  if (a < b)
    a = b;
}

// C++ 17に完全移行したら消す
// 最大公約数を求める
template <class T> T gcd(T n, T m) { return n ? gcd(m % n, n) : m; }

// 最小公倍数を求める
template <class T> T lcm(T n, T m) {
  int g = gcd(n, m);
  return n * m / g;
}

// 重複を消す。計算量はO(NlogN)
template <class T> void unique(std::vector<T> &v) {
  std::sort(v.begin(), v.end());
  v.erase(std::unique(v.begin(), v.end()), v.end());
}


#line 2 "tmp.cpp"

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int h, w;
  cin >> h >> w;
  ll K;
  cin >> K;
  int x1, y1, x2, y2;
  cin >> y1 >> x1 >> y2 >> x2;

  x1--;
  x2--;
  y1--;
  y2--;

  vector<string> grid(h);
  REP(i, h) { cin >> grid[i]; }

  constexpr ll M = numeric_limits<ll>::max();
  vector<ll> ans(h * w * 4, M);

  auto convert = [&](int x, int y, int k) -> int { return w * h * k + y * w + x; };

  int dx[4] = {1, 0, -1, 0};
  int dy[4] = {0, 1, 0, -1};

  priority_queue<pair<ll, tuple<int, int, int>>, vector<pair<ll, tuple<int, int, int>>>,
                 greater<pair<ll, tuple<int, int, int>>>>
      q;

  ans[convert(x1, y1, 0)] = 0;
  q.push({0, {x1, y1, 0}});

  while (!q.empty()) {
    auto p = q.top();
    q.pop();

    int x = get<0>(p.second);
    int y = get<1>(p.second);
    int k = get<2>(p.second);
    ll cost = ans.at(convert(x, y, k));

    if (cost < p.first) {
      continue;
    }

    // 目の前に進む場合
    int nx = x + dx[k];
    int ny = y + dy[k];
    if (0 <= nx && nx < w && 0 <= ny && ny < h && grid[ny][nx] == '.') {
      ll next_cost = p.first + 1LL;
      if (ans.at(convert(nx, ny, k)) > next_cost) {
        ans[convert(nx, ny, k)] = next_cost;
        q.push({next_cost, {nx, ny, k}});
      }
    }

    ll next_cost = K * ((p.first + K - 1) / K);
    if (ans[convert(x, y, (k + 1) % 4)] > next_cost) {
      ans[convert(x, y, (k + 1) % 4)] = next_cost;
      q.push({next_cost, {x, y, (k + 1) % 4}});
    }
  }

  ll ret = M;
  REP(i, 4) { chmin(ret, ans[convert(x2, y2, i)]); }
  cout << (ret == M ? -1 : (ret + K - 1) / K) << endl;

  return 0;
}


Measured memory_bytes: 41956