///////////////////////////////////////////////////////////////////////////////

#include <bits/stdc++.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>

using namespace std;

///////////////////////////////////////////////////////////////////////////////

#define DEBUG 0

#define pb push_back
#define V vector
#define M unordered_map
#define S static
#define PI  (3.1415926535)

#define rep(i,n) for(ll i=0LL; i<n; ++i)
#define srep(i,s,n) for(ll i=s; i<n; ++i)
#define rrep(i,n) for(ll i=n-1LL; i>=0LL; --i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define CIN(x) do { \
        assert(!cin.eof()); \
        cin >> x; \
        assert(!cin.fail()); \
} while(0);
#if DEBUG
#define debug_print(...) _debug_print(__VA_ARGS__)
#define debug_printf(...) printf(__VA_ARGS__)
#define debug_print_time _debug_print_time
#else // DEBUG
#define debug_print(...)
#define debug_printf(...)
#define debug_print_time
#endif // DEBUG

typedef long long ll;
typedef unsigned long long ull;
typedef tuple<ll, ll> t2;
typedef tuple<ll, ll, ll> t3;
typedef tuple<ll, ll, ll, ll> t4;
typedef tuple<ll, ll, ll, ll, ll> t5;
template <typename T>
using priority_queue_incr = priority_queue<T, V<T>, greater<T> >;

///////////////////////////////////////////////////////////////////////////////

template <typename TT, typename T>
T get_m(M<TT, T> &m, TT k, T default_value)
{
    if (m.find(k) == m.end()) return m[k] = default_value;
    return m[k];
}

template <typename TT, typename T>
void incr_m(M<TT, T> &m, TT k)
{
    if (m.find(k) == m.end()) m[k] = 0;
    m[k]++;
}

void llin(ll &a)
{
    CIN(a);
}

void llinl1(V<ll> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a;
        CIN(a);
        v.push_back(a);
    }
}

void llinl2(V<t2> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b;
        CIN(a >> b);
        v.push_back(t2(a, b));
    }
}

void llinl3(V<t3> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c;
        CIN(a >> b >> c);
        v.push_back(t3(a, b, c));
    }
}

void llinl4(V<t4> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c, d;
        CIN(a >> b >> c >> d);
        v.push_back(t4(a, b, c, d));
    }
}

void llina(V<ll> &v, ll count)
{
    llinl1(v, count);
}

template <typename T>
void sort(V<T> &v)
{
    sort(v.begin(), v.end());
}

template <typename T>
void sort_reverse(V<T> &v)
{
    sort(v.begin(), v.end(), greater<T>());
}

template <typename T>
void _debug_print(T x)
{
    cout << x << endl;
}

void _debug_print(const t2 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    cout << "-- " << x1 << " -- " << x2 << endl;
}

void _debug_print(const t3 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    cout << "-- " << x1 << " -- " << x2 << " -- " << x3 << endl;
}

void _debug_print(const t4 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    ll x4 = get<3>(x);
    cout << "-- " << x1 << " -- " << x2
         << " -- " << x3 << " -- " << x4 << endl;
}

template <typename T>
void _debug_print(T xarray[], ll n)
{
    rep (i, n) _debug_print(xarray[i]);
}

template <typename T>
void _debug_print(const V<T> &xlist)
{
    for (auto x : xlist) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename T>
void _debug_print(const set<T> &xset)
{
    for (auto x : xset) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename TT, typename T>
void _debug_print(const M<TT, T> &xlist)
{
    for (auto x : xlist) {
        TT k = x.first;
        T v = x.second;
        cout << "====" << endl;
        cout << "K=";
        _debug_print(k);
        cout << "V=";
        _debug_print(v);
    }
}

void _debug_print_time(const char *prefix)
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
    struct tm *tm = localtime(&tv.tv_sec);
    printf("-- %s %02d:%02d:%02d.%06ld\n",
           prefix, tm->tm_hour, tm->tm_min, tm->tm_sec, tv.tv_usec);
}

///////////////////////////////////////////////////////////////////////////////

void _main();
int main()
{
    cout << setprecision(12);
#if !DEBUG
    ios::sync_with_stdio(false);
    cin.tie(0);
#endif

    _main();
    return 0;
}

#define DIR_N  (0)
#define DIR_E  (1)
#define DIR_W  (2)
#define DIR_S  (3)

void _main()
{
    ll h; llin(h);
    ll w; llin(w);
    ll k; llin(k);
    ll x1; llin(x1); x1--;
    ll y1; llin(y1); y1--;
    ll x2; llin(x2); x2--;
    ll y2; llin(y2); y2--;
    S V<string> grid;
    rep (hh, h) {
        string tmp; CIN(tmp);
        grid.pb(tmp);
    }

    S priority_queue_incr<t5> q;

    ll ***swims = new ll**[4];
    rep (x, 4) {
        swims[x] = new ll*[h+1];
        rep (hh, h+1) swims[x][hh] = new ll[w+1];
        rep (hh, h+1) rep (ww, w+1) swims[x][hh][ww] = 1e18;
    }

    ll ***moves = new ll**[4];
    rep (x, 4) {
        moves[x] = new ll*[h+1];
        rep (hh, h+1) moves[x][hh] = new ll[w+1];
        rep (hh, h+1) rep (ww, w+1) moves[x][hh][ww] = 1e18;
    }

    q.push(t5(0, k, x1, y1, DIR_N));

    while (q.size()) {
        auto item = q.top(); q.pop();
        ll sswim = get<0>(item);
        ll mmove = get<1>(item);
        ll xx = get<2>(item);
        ll yy = get<3>(item);
        ll dir = get<4>(item);

        if (xx == x2 && yy == y2) {
            cout << sswim << endl;
            return;
        }

        if (swims[dir][xx][yy] < 1e17 && moves[dir][xx][yy] < 1e17) continue;
        swims[dir][xx][yy] = sswim;
        moves[dir][xx][yy] = mmove;

        if (xx > 0 && grid[xx-1][yy] == '.') {
            ll ns = sswim;
            ll nm = mmove + 1LL;
            if (mmove == k || dir != DIR_N) {
                ns++;
                nm = 1;
            }
            q.push(t5(ns, nm, xx-1, yy, DIR_N));
        }

        if (xx < h-1 && grid[xx+1][yy] == '.') {
            ll ns = sswim;
            ll nm = mmove + 1LL;
            if (mmove == k || dir != DIR_S) {
                ns++;
                nm = 1;
            }
            q.push(t5(ns, nm, xx+1, yy, DIR_S));
        }

        if (yy > 0 && grid[xx][yy-1] == '.') {
            ll ns = sswim;
            ll nm = mmove + 1LL;
            if (mmove == k || dir != DIR_W) {
                ns++;
                nm = 1;
            }
            q.push(t5(ns, nm, xx, yy-1, DIR_W));
        }

        if (yy < w-1 && grid[xx][yy+1] == '.') {
            ll ns = sswim;
            ll nm = mmove + 1LL;
            if (mmove == k || dir != DIR_E) {
                ns++;
                nm = 1;
            }
            q.push(t5(ns, nm, xx, yy+1, DIR_E));
        }
    }

    cout << -1 << endl;
}

///////////////////////////////////////////////////////////////////////////////


Measured memory_bytes: 129344