// #pragma GCC target ("avx")
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
using namespace std;
// #define int long long
// #define endl '\n'

#pragma region TEMPLATE

/* TYPE */
typedef long long ll;       typedef long double ld;
typedef pair<int, int> pii; typedef pair<ll, ll> pll;
typedef vector<pii> vpii;   typedef vector<pll> vpll;
typedef vector<int> vi;     typedef vector<ll> vl;
typedef vector<string> vst; typedef vector<bool> vb;
typedef vector<ld> vld;     typedef vector<vector<int>> vvi;
template<typename T, typename Cmp = less<>> using prique = priority_queue<T, vector<T>, Cmp>;
template<typename T> using prique_r = prique<T, greater<>>;
/* CONSTANT */
#define ln '\n'
const int INF = 1 << 30;    const ll INFF = 1LL << 60;  const string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const int MOD = 1e9 + 7;    const int MODD = 998244353; const string alphabet = "abcdefghijklmnopqrstuvwxyz";
const double EPS = 1e-9;    const ld PI = 3.14159265358979323846264338327950288;
const int dx[] = { 1, 0, -1,  0,  1, -1, -1, 1, 0 };
const int dy[] = { 0, 1,  0, -1, -1, -1,  1, 1, 0 };
/* CONTAINER */
#define PB              emplace_back
#define ALL(v)          (v).begin(), (v).end()
#define RALL(v)         (v).rbegin(), (v).rend()
#define SORT(v)         sort(ALL(v))
#define RSORT(v)        sort(RALL(v))
#define LESS(x, val)    (lower_bound(x.begin(), x.end(), val) - x.begin())
#define LEQ(x, val)     (upper_bound(x.begin(), x.end(), val) - x.begin())
#define GREATER(x, val) (int)(x).size() - LEQ((x), (val))
#define GEQ(x, val)     (int)(x).size() - LESS((x), (val))
#define UNIQUE(v)       sort(ALL(v)); (v).erase(unique(ALL(v)), (v).end())
template<typename T> vector<T> make_v(size_t a) { return vector<T>(a); }
template<typename T, typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...)); }
template<typename T, typename U, typename... V> enable_if_t<is_same<T, U>::value != 0> fill_v(U &u, const V... v) { u = U(v...); }
template<typename T, typename U, typename... V> enable_if_t<is_same<T, U>::value == 0> fill_v(U &u, const V... v) { for (auto &e : u) fill_v<T>(e, v...); }
/* LOOP */
#define _overload3(_1, _2, _3, name, ...) name
#define _REP(i, n)      REPI(i, 0, n)
#define REPI(i, a, b)   for (ll i = (ll)a; i < (ll)b; ++i)
#define REP(...)        _overload3(__VA_ARGS__, REPI, _REP,)(__VA_ARGS__)
#define _RREP(i, n)     RREPI(i, n, 0)
#define RREPI(i, a, b)  for (ll i = (ll)a; i >= (ll)b; --i)
#define RREP(...)       _overload3(__VA_ARGS__, RREPI, _RREP,)(__VA_ARGS__)
#define EACH(e, v)      for (auto& e : v)
#define PERM(v)         sort(ALL(v)); for (bool c##p = true; c##p; c##p = next_permutation(ALL(v)))
/* INPUT */
template<typename T> void SSS(T& t) { cin >> t; }
template<typename Head, typename... Tail> void SSS(Head&& head, Tail&&... tail) { cin >> head; SSS(tail...); }
#define SS(T, ...)      T __VA_ARGS__; SSS(__VA_ARGS__);
#define SV(T, v, n)     vector<T> v(n); for (auto& i : v) cin >> i;
#define SVV(T, v, n, m) vector<vector<T>> v(n, vector<T>(m)); for (auto& r : v) for (auto& i : r) cin >> i;
/* OUTPUT */
// Yes / No
inline int YES(bool x) { cout << (x ? "YES"  : "NO") << endl; return 0; }
inline int Yes(bool x) { cout << (x ? "Yes"  : "No") << endl; return 0; }
inline int yes(bool x) { cout << (x ? "yes"  : "no") << endl; return 0; }
inline int yES(bool x) { cout << (x ? "yES"  : "nO") << endl; return 0; }
inline int Yay(bool x) { cout << (x ? "Yay!" : ":(") << endl; return 0; }
// PROTOTYPE DECLARATION
template<typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &j);
template<typename... T> ostream &operator<<(ostream &os, const tuple<T...> &t);
template<class C, enable_if_t<!is_same<C, string>::value, decltype(declval<const C &>().begin(), nullptr)> = nullptr> ostream& operator<<(ostream &os, const C &c);
template<typename T> ostream &operator<<(ostream &os, const stack<T> &j);
template<typename T> ostream &operator<<(ostream &os, const queue<T> &j);
template<typename T, typename C, typename Cmp> ostream &operator<<(ostream &os, const priority_queue<T, C, Cmp> &j);
// IMPLEMENTATION
template<typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &j) { return os << '{' << j.first << ", " << j.second << '}'; }
template<size_t num = 0, typename... T> enable_if_t<num == sizeof...(T)> PRINT_TUPLE(ostream &os, const tuple<T...> &t) {}
template<size_t num = 0, typename... T> enable_if_t<num <  sizeof...(T)> PRINT_TUPLE(ostream &os, const tuple<T...> &t) { os << get<num>(t); if (num + 1 < sizeof...(T)) os << ", "; PRINT_TUPLE<num + 1>(os, t); }
template<typename... T> ostream &operator<<(ostream &os, const tuple<T...> &t) { PRINT_TUPLE(os << '{', t); return os << '}'; }
template<class C, enable_if_t<!is_same<C, string>::value, decltype(declval<const C &>().begin(), nullptr)>> ostream& operator<<(ostream &os, const C &c) { os << '{'; for (auto it = begin(c); it != end(c); it++) { if (begin(c) != it) os << ", "; os << *it; } return os << '}'; }
template<typename T> ostream &operator<<(ostream &os, const stack<T> &j) { deque<T> d; for (auto c = j; !c.empty(); c.pop()) d.push_front(c.top());  return os << d; }
template<typename T> ostream &operator<<(ostream &os, const queue<T> &j) { deque<T> d; for (auto c = j; !c.empty(); c.pop()) d.push_back(c.front()); return os << d; }
template<typename T, typename C, typename Cmp> ostream &operator<<(ostream &os, const priority_queue<T, C, Cmp> &j) { deque<T> d; for (auto c = j; !c.empty(); c.pop()) d.push_front(c.top());  return os << d; }
// OUTPUT FUNCTION
template<typename T> int PV(T &v) { int sz = v.size(); for (int i = 0; i < sz; ++i) cout << v[i] << " \n"[i == sz - 1]; return 0; }
inline int print() { cout << endl; return 0; }
template<typename Head> int print(Head&& head){ cout << head; return print(); }
template<typename Head, typename... Tail> int print(Head&& head, Tail&&... tail) { cout << head << " "; return print(forward<Tail>(tail)...); }
#ifdef LOCAL
inline void dump() { cerr << endl; }
template<typename Head> void dump(Head&& head) { cerr << head; dump(); }
template<typename Head, typename... Tail> void dump(Head&& head, Tail&&... tail) { cerr << head << ", "; dump(forward<Tail>(tail)...); }
#define debug(...) do {cerr << __LINE__ << ":\t" << #__VA_ARGS__ << " = "; dump(__VA_ARGS__); } while (false)
#else
#define dump(...)
#define debug(...)
#endif
/* OTHER */
#define fi              first
#define se              second
#define MP              make_pair
#define MT              make_tuple
#define tmax(x, y, z)   max((x), max((y), (z)))
#define tmin(x, y, z)   min((x), min((y), (z)))
template<typename T, typename A, typename B> inline bool between(T x, A a, B b) { return ((a <= x) && (x < b)); }
template<typename A, typename B> inline bool chmax(A &a, const B &b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A &a, const B &b) { if (a > b) { a = b; return true; } return false; }
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
inline ll POW(ll a, ll b) { ll r = 1; do { if (b & 1)  r *= a; a *= a; } while (b >>= 1); return r; }
struct abracadabra {
    abracadabra() {
        cin.tie(nullptr); ios::sync_with_stdio(false);
        cout << fixed << setprecision(20);
        cerr << fixed << setprecision(5);
    };
} ABRACADABRA;

#pragma endregion

vvi aaa;
 
void solve(int H, int W, int K, int x1, int y1, int x2, int y2, vector<string> &board) {
    auto dp = make_v<int>(H, W);
    REP(i, H) REP(j, W) dp[i][j] = INF / 3;
    dp[x2][y2] = 0;
 
    // [x, y, dis]
    queue<tuple<int, int, int>> Q;
    Q.emplace(x2, y2, 0);
    while (not Q.empty()) {
        auto [x, y, dis] = Q.front();
        Q.pop();
        bool up = true, dw = true, lf = true, rg = true;
        REP(i, K) {
            if (up) { // 上
                int nx = x - i - 1;
                if (nx < 0 or board[nx][y] == '@' or not chmin(dp[nx][y], dis + 1)) {
                    up = false;
                } else Q.emplace(nx, y, dis + 1);
            }
            if (dw) { // 下
                int nx = x + i + 1;
                if (nx >= H or board[nx][y] == '@' or not chmin(dp[nx][y], dis + 1)) {
                    dw = false;
                } else Q.emplace(nx, y, dis + 1);
            }
            if (lf) { // 左
                int ny = y - i - 1;
                if (ny < 0 or board[x][ny] == '@' or not chmin(dp[x][ny], dis + 1)) {
                    lf = false;
                } else Q.emplace(x, ny, dis + 1);
            }
            if (rg) { // 右
                int ny = y + i + 1;
                if (ny >= W or board[x][ny] == '@' or not chmin(dp[x][ny], dis + 1)) {
                    rg = false;
                } else Q.emplace(x, ny, dis + 1);
            }
            if (not (up or dw or lf or rg)) break;
        }
    }
    REP(i, H) REP(j, W) aaa[i][j] += dp[i][j];
}

void end() {
    cout << -1 << endl;
    exit(0);
}

struct Timer {
  chrono::high_resolution_clock::time_point st;

  Timer() { reset(); }

  void reset() {
    st = chrono::high_resolution_clock::now();
  }

  chrono::milliseconds::rep elapsed() {
    auto ed = chrono::high_resolution_clock::now();
    return chrono::duration_cast< chrono::milliseconds >(ed - st).count();
  }
};

signed main() {

    auto tm = Timer();


    SS(int, H, W, K);
    SS(int, x1, y1, x2, y2);
    --x1, --y1, --x2, --y2;
    SV(string, board, H);

    // H = 1000, W = 1000, K = 2;
    // board = vst(1000, string(1000, '.'));

    auto dp = make_v<int>(H, W);
    REP(i, H) REP(j, W) dp[i][j] = INF;
    dp[x1][y1] = 0;

    // [x, y, dis]
    queue<tuple<int, int, int>> Q;
    Q.emplace(x1, y1, 0);
    while (not Q.empty()) {
        if (tm.elapsed() > 2000) break;
        auto [x, y, dis] = Q.front();
        Q.pop();
        REP(i, K) { // 上
            int nx = x - i - 1;
            if (nx < 0) break;
            if (board[nx][y] == '@') break;
            if (not chmin(dp[nx][y], dis + 1)) continue;
            Q.emplace(nx, y, dis + 1);
        }
        REP(i, K) { // 下
            int nx = x + i + 1;
            if (nx >= H) break;
            if (board[nx][y] == '@') break;
            if (not chmin(dp[nx][y], dis + 1)) continue;
            Q.emplace(nx, y, dis + 1);
        }
        REP(i, K) { // 左
            int ny = y - i - 1;
            if (ny < 0) break;
            if (board[x][ny] == '@') break;
            if (not chmin(dp[x][ny], dis + 1)) continue;
            Q.emplace(x, ny, dis + 1);
        }
        REP(i, K) { // 右
            int ny = y + i + 1;
            if (ny >= W) break;
            if (board[x][ny] == '@') break;
            if (not chmin(dp[x][ny], dis + 1)) continue;
            Q.emplace(x, ny, dis + 1);
        }
    }

    // EACH(e, dp) EACH(f, e) if (f > INF / 2) f = -1;
    // EACH(e, dp) print(e);

    if (tm.elapsed() > 2000) {
        aaa = make_v<int>(H, W);
        REP(i, H) REP(j, W) aaa[i][j] = 0;
    
        solve(H, W, K, x1, y1, x2, y2, board);
        solve(H, W, K, x2, y2, x1, y1, board);
    
        ll res = INFF;
        REP(i, H) REP(j, W) chmin(res, aaa[i][j]);
        if (res > INF / 5) res = -1;
        print(res);
    } else {
        int res = dp[x2][y2];
        if (res > INF / 2) res = -1;
        print(res);
    }

}


Measured memory_bytes: 18192