// May this submission get accepted
#include <bits/stdc++.h>

// エイリアス
using  ll = long signed long;
using ull = long unsigned long;
using  ld = long double;
using namespace std;

// AtCoder/Codeforces 用 デバッグ検知
#ifdef ONLINE_JUDGE
constexpr bool DEBUG_MODE = false;
#else
constexpr bool DEBUG_MODE = true;
#endif

// エイリアス (補完・コンパイルが重くなる)
// #include <boost/multiprecision/cpp_int.hpp>
// using mll = boost::multiprecision::cpp_int;

// 汎用マクロ
#define ALLOF(x) (x).begin(), (x).end()
#define REP(i,n) for (long long i=0, i##_len=(n); i<i##_len; i++)
#define RANGE(i,is,ie) for (long long i=(is), i##_end=(ie); i<=i##_end; i++)
#define DSRNG(i,is,ie) for (long long i=(is), i##_end=(ie); i>=i##_end; i--)
#define STEP(i, is, ie, step) for (long long i=(is), i##_end=(ie), i##_step = (step); i<=i##_end; i+=i##_step)
#define UNIQUE(v) do { sort((v).begin(), (v).end()); (v).erase(unique((v).begin(), (v).end()), (v).end()); } while (false)
#define FOREACH(i,q) for (auto &i : q)
template<class T> bool chmax(T &a, const T b) { if (a < b) {a = b; return true;} return false; }
template<class T> bool chmin(T &a, const T b) { if (a > b) {a = b; return true;} return false; }
constexpr int INF = numeric_limits<int>::max();
constexpr long long LINF = numeric_limits<long long>::max();
constexpr long double EPS = 1e-10L;
#define Yes(q) ((q) ? "Yes" : "No")
#define YES(q) ((q) ? "YES" : "NO")
#define Possible(q) ((q) ? "Possible" : "Impossible")
#define POSSIBLE(q) ((q) ? "POSSIBLE" : "IMPOSSIBLE")
#define IIF(q,t,f) ((q) ? (t) : (f))
#define DUMP(q) DUMP_FUNC(q, #q, __FILE__, __LINE__)
template <typename T> void DUMP_PROC(T x) { if (is_integral<T>() || is_floating_point<T>()) cerr << "\e[32m" << x << "\e[m"; else cerr << x; }
template<> void DUMP_PROC<char>(char x) { cerr << "\e[36m\'" << x << "\'\e[m"; }
template<> void DUMP_PROC<string>(string x) { cerr << "\e[33m\"" << x << "\"\e[m"; }
template <typename T, typename U> void DUMP_PROC(pair<T, U> x) { cerr << "{"; DUMP_PROC(x.first); cerr << ", "; DUMP_PROC(x.second); cerr << "}"; }
template <typename ...T, typename U, U... Seq> void DUMP_PROC(tuple<T...> &x, integer_sequence<U, Seq...>) { (void)(int[]){(cerr << ((const char*[]){"", ", "})[!!Seq] << (DUMP_PROC(get<Seq>(x)), ""), 0)...}; }
template <typename ...T> void DUMP_PROC(tuple<T...> x) {cerr << "{"; DUMP_PROC(x, index_sequence_for<T...>()); cerr << "}";}
template <typename T> void DUMP_PROC(vector<T> x) { cerr << "["; for (auto &xi : x) { DUMP_PROC(xi); cerr << (&xi != &*x.rbegin()?", ":""); } cerr << "]"; }
template <typename T> void DUMP_FUNC(T x, const char* name, const char* fn, int ln) { cerr << "\e[32m[DEBUG]\e[m " << name << ": "; DUMP_PROC(x); cerr << " @ " << fn << "(" << ln << ")" << endl; }

// gcc拡張マクロ
#define popcount __builtin_popcount
#define popcountll __builtin_popcountll

// 標準入出力
struct qin { // query input
    size_t sz;
    qin(size_t _sz = 1) : sz(_sz) {}
    template <typename T> operator T () const { T a; cin >> a; return a; }
    template <typename T> operator vector<T> () const { vector<T> a(sz); for (size_t i = 0; i < sz; i++) cin >> a[i]; return a; }
    template <typename T, typename U> operator pair<T, U> () const { T f; U s; cin >> f >> s; return pair<T, U>(f, s); }
};
qin in1; // input one
template <typename T> void say(const T x, const char* end = "\n") { cout << x << end; }
void say(const ld x, const char* end = "\n") { cout << setprecision(30) << x << end; }
template <typename T> void say(const vector<T> x, const char* sep = " ", const char* end = "\n") { REP(i, x.size()) { cout << x[i] << (i+1 == i_len ? end : sep); } }
template <typename T> void say(const vector<vector<T>> x, const char* sep = " ", const char* end = "\n") { REP(i, x.size()) { say(x[i], sep, end); } }

// モジュール
// [[LIBRARY]]
// [[/LIBRARY]]

pair<ll, ll> dxy(ll d) {
    switch(d) {
        case 0: return {0, -1};
        case 1: return {0, +1};
        case 2: return {-1, 0};
        case 3: return {+1, 0};
    }
    return {0, 0};
}

// 処理内容
int main() {
    
    ios::sync_with_stdio(false); // stdioを使うときはコメントアウトすること
    cin.tie(nullptr);            // インタラクティブ問題ではコメントアウトすること
    
    ll h, w, k; cin >> h >> w >> k;
    ll x1, y1, x2, y2; cin >> x1 >> y1 >> x2 >> y2;
    x1--; y1--; x2--; y2--;
    vector<string> c = qin(h);

    vector d(h, vector(w, vector(4, tuple(LINF, LINF))));
    // deque<tuple<ll, ll, ll>> q;
    using T = tuple<ll, ll, ll, ll, ll>;
    priority_queue<T, vector<T>, greater<T>> q;
    REP(i, 4) {
        d[x1][y1][i] = {0, 0};
        // q.emplace_back(x1, y1, i);
        q.push(T(0, 0, x1, y1, i));
    }
    while (q.size()) {
        auto [r0, g0, x, y, i] = q.top(); q.pop();
        // auto [x, y, i] = q.front(); q.pop_front();
        auto [r, g] = d[x][y][i];
        if (pair<ll, ll>(r, g) != pair<ll, ll>(r0, g0)) continue;
        REP(j, 4) {
            auto [u, v] = dxy(j);
            u += x; v += y;
            if (0 <= u && u < h && 0 <= v && v < w && c[u][v] == '.') {
                ll r2 = r, g2 = g;
                if (i != j) {
                    if (k == 1) {
                        g2 = 0;
                        r2++;
                    } else {
                        r2 += (g2 + k - 1) / k;
                        g2 = 1;
                    }
                } else {
                    g2++;
                    if (g2 == k) {
                        g2 = 0;
                        r2++;
                    }
                }
                if (chmin(d[u][v][j], tuple(r2, g2))) {
                    // if (go_front) {
                    //     q.emplace_front(u, v, j);
                    // } else {
                    //     q.emplace_back(u, v, j);
                    // }
                    q.push(T(r2, g2, u, v, j));
                }
            }
        }
    }

    // REP(i, h) REP(j, w) {
    //     ll v = LINF;
    //     REP(k, 4) {
    //         auto [r, g] = d[i][j][k];
    //         if (r == LINF) continue;
    //         chmin(v, r + !!g);
    //     }
    //     if (v == LINF) {
    //         cerr << " ";
    //     } else {
    //         cerr << v;
    //     }
    //     if (j+1 == w)
    //         cerr << "\n";
    // }

    ll ans = LINF;
    REP(i, 4) {
        auto [r, g] = d[x2][y2][i];
        if (r == LINF) continue;
        chmin(ans, r + !!g);
    }
    if (ans == LINF) {
        say(-1);
    } else {
        say(ans);
    }
    
}

Measured memory_bytes: 207244