#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <array>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <stack>
#include <queue>
#include <bitset>
#include <tuple>
#include <cmath>
#include <complex>
#include <algorithm>
#include <utility>
#include <regex>
#include <cstdint>
#include <numeric>
#include <functional>
#include <cassert>

using namespace std;
using ll  = long long;
using ull = unsigned long long;

namespace utils{
#define ALL(x) begin(x), end(x)
#define RALL(x) rbegin(x), rend(x)
    template<class T, class Compare> using p_queue = priority_queue<T, vector<T>, Compare>;
    template<class T> using min_queue = p_queue<T, greater<T>>;
    template<class T> using max_queue = p_queue<T, less<T>>;

    template<class T> inline bool UPMIN(T& X, const T& A){ if(X > A) {X = A; return true;} return false; }
    template<class T> inline bool UPMAX(T& X, const T& A){ if(X < A) {X = A; return true;} return false; }

    template<class T>
    vector<T> VEC(int n, T t){
        return vector<T>(n, t);
    }
    template<class ...Ts>
    auto VEC(int n, Ts ... ts){
        return vector<decltype(VEC(ts...))>(n, VEC(ts...));
    }

    template <class S, class T>
    istream& operator>>(istream& is, tuple<S, T>& t){
        return is >> get<0>(t) >> get<1>(t);
    }

    template <class S, class T, class U>
    istream& operator>>(istream& is, tuple<S, T, U>& t){
        return is >> get<0>(t) >> get<1>(t) >> get<2>(t);
    }

    template <class S, class T>
    ostream& operator<<(ostream& os, const tuple<S, T>& t){
        return os << get<0>(t) << ' ' <<  get<1>(t);
    }

    template <class S, class T, class U>
    ostream& operator<<(ostream& os, const tuple<S, T, U>& t){
        return os << get<0>(t) << ' ' <<  get<1>(t) << ' ' <<  get<2>(t);
    }

    template<class T>
    istream& operator>>(istream& is, vector<T>& v){
        for (auto &&x : v) { is >> x; } return is;
    }

    template<class T>
    ostream& operator<<(ostream& os, const vector<T>& v){
        auto p = v.begin();
        assert(p != v.end());
        os << *p++;
        while(p != v.end()){
            os << ' ' << *p++;
        }
        return os ;
    }

    template<class T>
    ostream& operator<<(ostream& os, const vector<vector<T>>& v){
        auto p = v.begin();
        assert(p != v.end());
        os << *p++;
        while(p != v.end()){
            os << '\n' << *p++;
        }
        return os;
    }

    template<class ...Ts>
    ostream& operator<<(ostream& os, const vector<tuple<Ts...>>& v){
        auto p = v.begin();
        assert(p != v.end());
        os << *p++;
        while(p != v.end()){
            os << '\n' << *p++;
        }
        return os;
    }

    constexpr long long INFLL   = 1'000'000'000'000'000'000ll;
    constexpr int       INF     = 1'000'000'000;
    constexpr double    PI      = 3.14'159'265'358'973;
    constexpr double    EPS     = 1e-10;
}
using namespace utils;

template<class Monoid>
class SegmentTree {
    using Func = std::function<Monoid(Monoid, Monoid)>;
    int N;

    std::vector<Monoid> segment;

    const Func op;
    const Monoid id;

    bool dirty_flag;
public:
    // id : op = max なら -INT_MAX
    SegmentTree(int n, const Func biop, const Monoid& M1)
    : op(biop), id(M1), dirty_flag(false) {
        N = 1;
        while(N < n) N *= 2;
        segment.assign(2 * N, id);
    }

    void set(int k, const Monoid &a){
        dirty_flag = true;
        segment[k + N] = a;
    }

    void build() {
        for (int k = N - 1; k > 0; --k) {
            segment[k] = op(segment[2 * k], segment[2 * k + 1]);
        } // end k
        dirty_flag = false;
    }

    void update(int k, const Monoid& a){
        k += N;
        segment[k] = a;
        while(k /= 2){
            segment[k] = op(segment[k*2], segment[k*2+1]);
        }
    }

    // -> op [a,b)
    Monoid query(unsigned a, unsigned b){
        if(dirty_flag) build();
        dirty_flag = false;
        Monoid L = id, R = id;
        for (a += N, b += N; a < b; a >>= 1u, b >>= 1u) {
            if(a & 1u) L = op(L, segment[a++]);
            if(b & 1u) R = op(segment[--b], R);
        } // end i
        return op(L, R);
    }

    Monoid operator[](const int &k) const{
        return segment[k + N];
    }
};


class solver{
    istream& is;
    ostream& os;

public:
    solver(istream& I, ostream& O) :is(I), os(O) {}

    int H, W, K;
    int x1, y1, x2, y2;
    vector<vector<char>> ike;

    vector<SegmentTree<bool>> hvs, wvs;

    bool input() {
        is >> H >> W >> K;
        is >> x1 >> y1 >> x2 >> y2;
        hvs.reserve(H);
        for (int i = 0; i < H; ++i) {
            hvs.emplace_back(W, [](bool a, bool b){return a && b;}, true);
        } // end i
        wvs.reserve(W);
        for (int i = 0; i < W; ++i) {
            wvs.emplace_back(H, [](bool a, bool b){return a && b;}, true);
        } // end i
        x1--;y1--;x2--;y2--;
        ike = VEC(H, W, '\0');
        is >> ike;
        for (int i = 0; i < H; ++i) {
            for (int j = 0; j < W; ++j) {
                hvs[i].set(j, ike[i][j] == '.');
                wvs[j].set(i, ike[i][j] == '.');
            } // end j
        } // end i
        for (int i = 0; i < H; ++i) {
            hvs[i].build();
        } // end i
        for (int i = 0; i < W; ++i) {
            wvs[i].build();
        } // end i
        return !!is;
    }

    bool inside(int x, int y) const{
        return 0 <= x and x < H and 0 <= y and y < W;
    }

    bool lotus(int x, int y) const {
        return ike[x][y] == '@';
    }

    int maxgo(int i, int x, int y){
        int ok = 0;
        int ng = K+1;
        if(i % 2){
            while(abs(ok - ng) > 1){
                int mid = (ok + ng) / 2;
                int nx = x + dx[i] * mid;
                if(inside(nx, y) and wvs[y].query(min(nx, x), max(nx, x)+1)){
                    ok = mid;
                }
                else ng = mid;
            }
        }
        else{
            while(abs(ok - ng) > 1){
                int mid = (ok + ng) / 2;
                int ny = y + dy[i] * mid;
                if(inside(x, ny) and hvs[x].query(min(ny, y), max(ny, y)+1)){
                    ok = mid;
                }
                else ng = mid;
            }
        }
        return ok;
    }


    vector<int> dx = {0, 1, 0, -1};
    vector<int> dy = {1, 0, -1, 0};

    void run();
};

int main(int argc, char *argv[]) {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << setprecision(16) << scientific;
#ifdef XELMH
    string test_cases = "test_F.txt";
    cerr << test_cases << " -->" << endl;
    auto fs = fstream(test_cases, fstream::in);
    int loop = 0;
    while(fs) {
        loop++;
        cout << '#' << loop << "#------\n";
        solver(fs, cout).run();
    }
    if(loop <= 1) {
        cout << "===" << endl;
        while(cin) solver(cin, cout).run();
    }
#else
    solver(cin, cout).run();
#endif
    return 0;
}


void solver::run(){
    if(!input()) return;
    auto distance = VEC( 4, H, W,  INF);
    // (distance, x, y, direction)
    queue<tuple<int, int, int>> pq;
    for (int i = 0; i < 4; ++i) {
        distance[i][x1][y1] = 0;
        int mx = maxgo(i, x1, y1);
        for (int k = mx; k > 0; --k) {
            int nx, ny;
            nx = x1 + dx[i]*k;
            ny = y1 + dy[i]*k;

            distance[i][nx][ny] = 1;
            pq.emplace(nx, ny, i);
        } // end k
    } // end i

    while(!pq.empty()){
        int x, y, direction;
        tie(x, y, direction) = pq.front();pq.pop();
        int need = distance[direction][x][y];
        for (int i = 0; i < 4; ++i) {
            int mx = maxgo(i, x, y);
            for (int k = mx; k > 0; --k) {
                int nx, ny;
                nx = x + dx[i]*k;
                ny = y + dy[i]*k;

                if(UPMIN(distance[i][nx][ny], need + 1)){
                    pq.emplace(nx, ny, i);
                }
                else break;
            } // end k
        } // end i
    }
    int ans = INF;
    for (int i = 0; i < 4; ++i) {
        UPMIN(ans, distance[i][x2][y2]);
    } // end i
//    cerr << distance << endl;
    if(ans == INF){
        cout << -1 << endl;
    }
    else cout << ans << endl;
}


Measured memory_bytes: 141236