#define _USE_MATH_DEFINES
#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define reps(i, n) for (int i = 1; i <= (n); ++i)
#define repd(i, n) for (int i = (n)-1; i >= 0; --i)
#define repds(i, n) for (int i = (n); i > 0; --i)
#define loop(i, x, n) for (int i = (x); i < (n); ++i)
#define loops(i, x, n) for (int i = (x); i <= (n); ++i)
#define loopd(i, x, n) for (int i = (x); i > (n); --i)
#define loopds(i, x, n) for (int i = (x); i >= (n); --i)
#define itrep(i, a) for (auto i = begin(a); i != end(a); ++i)
#define itrepd(i, a) for (auto i = rbegin(a); i != rend(a); ++i)
#define each(i, x) for (auto &&i : x)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(a) ((int)a.size())
#define pow2(n) (n * n)
#define int ll
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
template <class T>
using priority_queuel = priority_queue<T, vector<T>, greater<T>>;
constexpr ll inf = static_cast<ll>(1e18);
constexpr int iinf = static_cast<int>(1e9);
constexpr double dinf = 1e10;
constexpr ld ldinf = 1e18;
constexpr double eps = 1e-9;
ll mod = static_cast<ll>(1e9 + 7);
template <class T, class... Args>
constexpr void mins(T &a, Args... args) { a = min<T>({a, args...}); }
template <class T, class... Args>
constexpr void maxs(T &a, Args... args) { a = max<T>({a, args...}); }
template <class F>
class FixPoint : private F {
public:
    explicit constexpr FixPoint(F &&f) : F(std::forward<F>(f)) {}
    template <class... Args>
    constexpr decltype(auto) operator()(Args &&... args) const { return F::operator()(*this, std::forward<Args>(args)...); }
};
template <class F>
constexpr decltype(auto) funcs(F &&f) { return FixPoint<F>{std::forward<F>(f)}; }
template <class T>
std::vector<T> vecs(int n, T &&val) { return std::vector<T>(std::forward<int>(n), std::forward<T>(val)); }
template <class... Args>
decltype(auto) vecs(int n, Args &&... args) { return std::vector<decltype(vecs(std::forward<Args>(args)...))>(std::forward<int>(n), vecs(std::forward<Args>(args)...)); }
template <class V, class T>
void fill(V &x, const T &val) { x = val; }
template <class V, class T>
void fill(vector<V> &vec, const T &val) {
    for (auto &&v : vec)
        fill(v, val);
}

template <class T, class U>
struct fpair {
    T first;
    U second;
    fpair(T fi = T(), U se = U()) : first(fi), second(se) {}
    bool operator<(const fpair &x) const {
        return first < x.first;
    }
    bool operator>(const fpair &x) const {
        return first > x.first;
    }
};

void solve() {
    int h, w, k;
    cin >> h >> w >> k;
    int sx, sy, gx, gy;
    cin >> sx >> sy >> gx >> gy;
    --sx, --sy, --gx, --gy;
    vector<string> c(h);
    rep(i, h) cin >> c[i];

    auto toId = [&](int x, int y, int z) {
        return w * x + y + h * w * z;
    };
    auto ceilK = [&](int val) {
        return (val + k - 1) / k * k;
    };

    int dx[] = {1, 0, -1, 0};
    int dy[] = {0, 1, 0, -1};
    vector<int> d(h * w * 4, inf);
    priority_queuel<fpair<int, int>> que;
    d[toId(sx, sy, 0)] = 0;
    que.emplace(0, toId(sx, sy, 0));
    while (!que.empty()) {
        auto p = que.top();
        que.pop();
        int v = p.second;
        if (d[v] != p.first) continue;
        int z = v / (h * w);
        int x = (v - (h * w) * z) / w;
        int y = (v - (h * w) * z) % w;
        rep(i, 4) {
            int nv = toId(x, y, i);
            if (d[nv] > ceilK(d[v])) {
                d[nv] = ceilK(d[v]);
                que.emplace(d[nv], nv);
            }
        }

        int nx = x + dx[z];
        int ny = y + dy[z];
        int nv = toId(nx, ny, z);
        if (nx < 0 || nx >= h || ny < 0 || ny >= w || c[nx][ny] == '@') continue;
        if (d[nv] > d[v] + 1) {
            d[nv] = d[v] + 1;
            que.emplace(d[nv], nv);
        }
    }

    int ans = inf;
    rep(i, 4) mins(ans, d[toId(gx, gy, i)]);
    cout << (ans < inf ? (ans + k - 1) / k : -1) << endl;
}

signed main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    solve();
    cout.flush();
    return 0;
}

Measured memory_bytes: 44112