#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

ll H, W, K;
ll SX, SY, TX, TY;
vector<vector<bool>> L;
queue<pair<ll, ll>> Q;
vector<vector<ll>> D;
const ll INF = 1ll << 60;
const ll DX[] = {0, 1, 0, -1};
const ll DY[] = {1, 0, -1, 0};

int main() {
  cin >> H >> W >> K;
  cin >> SX >> SY >> TX >> TY;
  L.resize(H + 2);
  for (auto &Lx : L) Lx.resize(W + 2, true);
  for (ll x = 1; x <= H; ++x) {
    for (ll y = 1; y <= W; ++y) {
      char c;
      cin >> c;
      if (c == '.') L[x][y] = false;
    }
  }
  D.resize(H + 2);
  for (auto &Dx : D) {
    Dx.resize(W + 2, INF);
  }
  Q.push({SX, SY});
  D[SX][SY] = 0;
  while (!Q.empty()) {
    ll x, y;
    tie(x, y) = Q.front();
    Q.pop();
    ll d = D[x][y];
    for (ll i = 0; i < 4; ++i) {
      ll dx = DX[i], dy = DY[i];
      for (ll j = 1; j <= K; ++j) {
        ll x2 = x + j * dx;
        ll y2 = y + j * dy;
        if (L[x2][y2]) break;
        if (D[x2][y2] <= d) break;
        if (D[x2][y2] == d + 1) continue;
        Q.push({x2, y2});
        D[x2][y2] = d + 1;
      }
    }
  }
  ll res = D[TX][TY];
  cout << (res == INF ? -1 : res) << endl;
  return 0;
}
