#include <bits/stdc++.h>
using namespace std;
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#ifdef LOCAL
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) { cerr << ' ' << H; debug_out(T...); }
#define debug(...) cerr << 'L' << __LINE__ << " [" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif
template<typename T> using V = vector<T>;
template<typename T> using P = pair<T, T>;
using ll = long long;
using ld = long double;
using Vi = V<int>;  using VVi = V<Vi>;
using Vl = V<ll>;   using VVl = V<Vl>;
using Vd = V<ld>;   using VVd = V<Vd>;
using Vb = V<bool>; using VVb = V<Vb>;
using Pi = P<int>;
using Pl = P<ll>;
using Pd = P<ld>;
template<typename T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<typename T> inline int sz(T &x) { return x.size(); }
template<typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
template<typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { os << '(' << p.first << ", " << p.second << ')'; return os; }
template<typename T> istream &operator>>(istream &is, vector<T> &v) { for (auto &e : v) is >> e; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<typename T> inline int count_between(vector<T> &a, T l, T r) { return lower_bound(all(a), r) - lower_bound(all(a), l); } // [l, r)
inline ll cDiv(const ll x, const ll y) { return (x+y-1) / y; } // ceil(x/y)
inline int fLog2(const ll x) { assert(x > 0); return 63-__builtin_clzll(x); } // floor(log2(x))
inline int cLog2(const ll x) { assert(x > 0); return (x == 1) ? 0 : 64-__builtin_clzll(x-1); } // ceil(log2(x))
inline int popcount(const ll x) { return __builtin_popcountll(x); }
inline void fail() { cout << -1 << '\n'; exit(0); }
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
// const int INF  = 1<<30;
const ll INFll = 1ll<<60;
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
// const int MOD  = int(1e9)+7;
// const int MOD  = 998244353;


// const array<int, 2> dx = {1, 0};
// const array<int, 2> dy = {0, 1};
const array<int, 4> dx = {1, 0, -1, 0};
const array<int, 4> dy = {0, 1, 0, -1};


int main() {
  ll h, w, k; cin >> h >> w >> k;
  int si, sj, ti, tj; cin >> si >> sj >> ti >> tj;
  --si, --sj, --ti, --tj;
  vector<string> F(h);
  rep(i, h) cin >> F[i];

  auto dist = make_vec(4, h, w, INFll);
  priority_queue_rev<pair<ll, tuple<int, int, int>>> pq;
  rep(i, 4) {
    dist[0][si][sj] = 0;
    pq.emplace(0, make_tuple(i, si, sj));
  }
  
  while (!pq.empty()) {
    auto [d, u]  = pq.top(); pq.pop();
    auto [di, i, j] = u;
    if (dist[di][i][j] < d) continue;
    rep(dir, sz(dx)) {
      int ii = i + dx[dir];
      int jj = j + dy[dir];
      if (ii < 0 || ii >= h || jj < 0 || jj >= w) continue;
      if (F[ii][jj] == '@') continue;
      ll res = -1;
      if (di == dir) res = d + 1;
      else res = cDiv(d, k) * k  + 1;
      if (chmin(dist[dir][ii][jj], res)) {
        pq.emplace(res, make_tuple(dir, ii, jj));
      }
    }
  }

  ll ans = INFll;
  rep(i, 4) chmin(ans, dist[i][ti][tj]);
  cout << (ans == INFll ? -1 : cDiv(ans, k)) << '\n';
}

Measured memory_bytes: 49572