#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
// #define int long long
// #define double long double
#define rep(i,n) for (int i=0; i<(int)(n); ++i)
#define rep1(i,n) for (int i=1; i<(int)(n); ++i)
#define repeq(i,n) for (int i=0; i<=(int)(n); ++i)
#define rep1eq(i,n) for (int i=1; i<=(int)(n); ++i)
#define rrep(i,n) for (int i=(int)(n)-1; i>=0; --i)
#define rrep1(i,n) for (int i=(int)(n)-1; i>0; --i)
#define rrepeq(i,n) for (int i=(int)(n); i>=0; --i)
#define rrep1eq(i,n) for (int i=(int)(n); i>0; --i)
#define REP(i,a,b) for (int i=(int)(a); i<=(int)(b); ++i)
#define RREP(i,a,b) for (int i=(int)(a); i>=(int)(b); --i)
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
template<typename T> using Graph = vector<vector<T>>;
template<typename T> using Spacial = vector<vector<vector<T>>>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template<typename T> using greater_priority_queue = priority_queue<T, vector<T>, greater<T>>;
const int MOD = 1e9+7;
const int MOD2 = 998244353;
// const double EPS = 1e-9;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
string interval[2] = {" ", "\n"}; // {" ", "\n"}

template<typename T> struct is_plural : false_type{};
template<typename T1, typename T2> struct is_plural<pair<T1, T2>> : true_type{};
template<typename T> struct is_plural<vector<T>> : true_type{};
template<typename T> struct is_plural<complex<T>> : true_type{};
 
template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << " " << p.second; }
template<typename T> istream &operator>>(istream &is, vector<T> &vec) { for (auto itr = vec.begin(); itr != vec.end(); ++itr) is >> *itr; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec) { if (vec.empty()) return os; bool pl = is_plural<T>(); os << vec.front(); for (auto itr = ++vec.begin(); itr != vec.end(); ++itr) os << interval[pl] << *itr; return os; }
 
bool CoutYN(bool a, string y = "Yes", string n = "No") { cout << (a ? y : n) << "\n"; return a; }

template<typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template<typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

long long modpow(int a, long long n, int mod = MOD) { long long ret = 1; do { if (n & 1) ret = ret * a % mod; a = 1LL * a * a % mod; } while (n >>= 1); return ret; }

template<typename T> T GCD(T a, T b) { return b ? GCD(b, a%b) : a; }
template<typename T> T LCM(T a, T b) { return a / GCD(a, b) * b; }

template<typename T1, typename T2> bool CompareBySecond(pair<T1, T2> a, pair<T1, T2> b) { return a.second != b.second ? a.second < b.second : a.first < b.first; }
template<typename T1, typename T2> bool CompareByInverse(pair<T1, T2> a, pair<T1, T2> b) { return a.first != b.first ? a.first < b.first : a.second > b.second; }


/* -------- <templates end> -------- */


struct Point {
  int x, y;

  friend istream &operator>>(istream &is, Point &p) {
    is >> p.x >> p.y;
    p.x--, p.y--;
    return is;
  }
};

struct direction {
  bool e, w, s, n;

  direction() : e(true), w(true), s(true), n(true) {}
};

const int INFTY = 1e8;

void solve() {
  int h, w, k; cin >> h >> w >> k;
  Point s, t; cin >> s >> t;
  vector<string> g(h); cin >> g;

  Graph<direction> explore(h, vector<direction>(w));
  Graph<int> memo(h, vi(w, INFTY));
  queue<Point> q;
  q.emplace(s);
  memo[s.x][s.y] = 0;

  while (!q.empty()) {
    auto v = q.front(); q.pop();
    int d = memo[v.x][v.y];

    if (explore[v.x][v.y].e) {
      rep1eq(i,k) {
        if (v.y + i == w || g[v.x][v.y + i] == '@') break;
        if (memo[v.x][v.y + i] <= d) break;
        if (!explore[v.x][v.y + i].e) break;
        if (chmin(memo[v.x][v.y + i], d + 1)) q.emplace(Point{v.x, v.y + i});
        if (i != k) explore[v.x][v.y + i].e = false;
        explore[v.x][v.y + i].w = false;
      }
    }

    if (explore[v.x][v.y].w) {
      rep1eq(i,k) {
        if (v.y - i == -1 || g[v.x][v.y - i] == '@') break;
        if (memo[v.x][v.y - i] <= d) break;
        if (!explore[v.x][v.y - i].w) break;
        if (chmin(memo[v.x][v.y - i], d + 1)) q.emplace(Point{v.x, v.y - i});
        if (i != k) explore[v.x][v.y - i].w = false;
        explore[v.x][v.y - i].e = false;
      }
    }

    if (explore[v.x][v.y].s) {
      rep1eq(i,k) {
        if (v.x + i == h || g[v.x + i][v.y] == '@') break;
        if (memo[v.x + i][v.y] <= d) break;
        if (!explore[v.x + i][v.y].s) break;
        if (chmin(memo[v.x + i][v.y], d + 1)) q.emplace(Point{v.x + i, v.y});
        if (i != k) explore[v.x + i][v.y].s = false;
        explore[v.x + i][v.y].n = false;
      }
    }

    if (explore[v.x][v.y].n) {
      rep1eq(i,k) {
        if (v.x - i == -1 || g[v.x - i][v.y] == '@') break;
        if (memo[v.x - i][v.y] <= d) break;
        if (!explore[v.x - i][v.y].n) break;
        if (chmin(memo[v.x - i][v.y], d + 1)) q.emplace(Point{v.x - i, v.y});
        if (i != k) explore[v.x - i][v.y].n = false;
        explore[v.x - i][v.y].s = false;
      }
    }
  }

  if (memo[t.x][t.y] == INFTY) cout << -1 << endl;
  else cout << memo[t.x][t.y] << endl;
}


/* -------- <programs end> -------- */


signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  solve();
  return 0;
}


Measured memory_bytes: 16040