#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define ALL(x) (x).begin(), (x).end()
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template<typename T> void ndarray(vector<T> &vec, int len) { vec.resize(len); }
template<typename T, typename... Args> void ndarray(vector<T> &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) ndarray(v, args...); }
template<typename T> bool chmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template<typename T> bool chmin(T &m, const T q) { if (m > q) {m = q; return true;} else return false; }
template<typename T1, typename T2> pair<T1, T2> operator+(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first + r.first, l.second + r.second); }
template<typename T1, typename T2> pair<T1, T2> operator-(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first - r.first, l.second - r.second); }
template<typename T> istream &operator>>(istream &is, vector<T> &vec){ for (auto &v : vec) is >> v; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec){ os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const deque<T> &vec){ os << "deq["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa){ os << "(" << pa.first << "," << pa.second << ")"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl;

int main()
{
    int H, W, K;
    cin >> H >> W >> K;
    int x1, y1, x2, y2;
    cin >> x1 >> y1 >> x2 >> y2;
    x1--, x2--, y1--, y2--;

    vector<string> C(H);
    cin >> C;

    constexpr int INF = 1e9;
    vector visited(H, vector<int>(W));
    visited[x1][y1] = 1;
    queue<pint> q;
    q.emplace(x1, y1);

    FOR(t, 1, 1e7)
    {
        if (q.empty()) break;
        unordered_map<int, vector<int>> x2y, y2x;
        while (q.size())
        {
            auto [x, y] = q.front();
            q.pop();
            x2y[x].emplace_back(y);
            y2x[y].emplace_back(x);
        }

        set<pint> nxt;
        for (auto p : x2y)
        {
            int x = p.first;
            vector<int> ys = p.second;
            sort(ys.begin(), ys.end());
            REP(i, ys.size())
            {
                int yend = min(ys[i] + K + 1, (i + 1 < ys.size() ? ys[i + 1] : W));
                int y = ys[i];
                while (y < yend)
                {
                    if (C[x][y] == '@') break;
                    if (chmax(visited[x][y], 1)) nxt.emplace(x, y);
                    y++;
                }
                yend = max(ys[i] - K - 1, (i ? ys[i - 1] : -1));
                y = ys[i];
                while (y > yend)
                {
                    if (C[x][y] == '@') break;
                    if (chmax(visited[x][y], 1)) nxt.emplace(x, y);
                    y--;
                }
            }
        }

        swap(H, W);
        for (auto p : y2x)
        {
            int x = p.first;
            vector<int> ys = p.second;
            sort(ys.begin(), ys.end());
            REP(i, ys.size())
            {
                int yend = min(ys[i] + K + 1, (i + 1 < ys.size() ? ys[i + 1] : W));
                int y = ys[i];
                while (y < yend)
                {
                    if (C[y][x] == '@') break;
                    if (chmax(visited[y][x], 1)) nxt.emplace(y, x);
                    y++;
                }
                yend = max(ys[i] - K - 1, (i ? ys[i - 1] : -1));
                y = ys[i];
                while (y > yend)
                {
                    if (C[y][x] == '@') break;
                    if (chmax(visited[y][x], 1)) nxt.emplace(y, x);
                    y--;
                }
            }
        }
        swap(H, W);

        if (visited[x2][y2])
        {
            cout << t << '\n';
            return 0;
        }

        for (auto x : nxt)
            q.emplace(x);
    }
    puts("-1");
}


Measured memory_bytes: 15324