//https://vjudge.net/contest/381915#problem
#include <bits/stdc++.h>
using namespace std;

#define el '\n'
#define pb push_back
#define sp ' '
#define all(x) (x).begin(), (x).end()
#define mset(x, y) memset(x, y, sizeof(x))
#define ff first
#define ss second

// clang-format off
bool chmin(int& a, int b){ return b < a ? a = b, true : false; }
bool chmax(int& a, int b){ return b > a ? a = b, true : false; }
bool chmin(long long& a, long long b){ return b < a ? a = b, true : false; }
bool chmax(long long& a, long long b){ return b > a ? a = b, true : false; }
#ifndef ONLINE_JUDGE
template <typename T, size_t N> int SIZE(const T (&t)[N]){ return N; } template<typename T> int SIZE(const T &t){ return t.size(); } string to_string(const string s, int x1=0, int x2=1e9){ return '"' + ((x1 < (int)s.size()) ? s.substr(x1, x2-x1+1) : "") + '"'; } string to_string(const char* s) { return to_string((string) s); } string to_string(const bool b) { return (b ? "true" : "false"); } string to_string(const char c){ return string({c}); } template<size_t N> string to_string(const bitset<N> &b, int x1=0, int x2=1e9){ string t = ""; for(int __iii__ = min(x1,SIZE(b)),  __jjj__ = min(x2, SIZE(b)-1); __iii__ <= __jjj__; ++__iii__){ t += b[__iii__] + '0'; } return '"' + t + '"'; } template <typename A, typename... C> string to_string(const A (&v), int x1=0, int x2=1e9, C... coords); int l_v_l_v_l = 0, t_a_b_s = 0; template <typename A, typename B> string to_string(const pair<A, B> &p) { l_v_l_v_l++; string res = "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; l_v_l_v_l--; return res; } template <typename A, typename... C> string to_string(const A (&v), int x1, int x2, C... coords) { int rnk = rank<A>::value; string tab(t_a_b_s, ' '); string res = ""; bool first = true; if(l_v_l_v_l == 0) res += el; res += tab + "["; x1 = min(x1, SIZE(v)), x2 = min(x2, SIZE(v)); auto l = begin(v); advance(l, x1); auto r = l; advance(r, (x2-x1) + (x2 < SIZE(v))); for (auto e = l; e != r; e = next(e)) { if (!first) { res += ", "; } first = false; l_v_l_v_l++; if(e != l){ if(rnk > 1) { res += el; t_a_b_s = l_v_l_v_l; }; } else{ t_a_b_s = 0; } res += to_string(*e, coords...); l_v_l_v_l--; } res += "]"; if(l_v_l_v_l == 0) res += el; return res; } void dbgm(){;} template<typename Heads, typename... Tails> void dbgm(Heads H, Tails... T){ cout << to_string(H) << " | "; dbgm(T...); } 
#define dbg(...) cout << "[" << #__VA_ARGS__ << "]: "; cout << to_string(__VA_ARGS__) << endl
#define dbgm(...) cout << "[" << #__VA_ARGS__ << "]: "; dbgm(__VA_ARGS__); cout << endl
#else
#define dbg(...) ;
#define dbgm(...) ;
#endif
// clang-format on

typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, pii> ppi;
typedef pair<ll, ll> pll;
typedef pair<int, ll> pil;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef vector<pll> vpll;
typedef vector<vpii> vvpii;
typedef vector<vpll> vvpll;

const int inf = 1e09 + 5e3;
const ll linf = 2e18 + 5e3;
const int mod = 1e9 + 7;
const int mxn = 1e5 + 30;

int h, w, k;
pii start, target;
vvi maz;

int dx[] = {0, 1, 0, -1};
int dy[] = {1, 0, -1, 0};

inline bool check(pii a) { return a.ff < h && a.ss < w && a.ff >= 0 && a.ss >= 0; }

ll bfs()
{
    vector<vector<vector<pii>>> dist(h, vector<vector<pii>>(w, vector<pii>(4, pii(inf, inf)))); // i, j , dir/ n s e w
    multiset<vector<int>> q;
    for (int z = 0; z < 4; z++)
    {
        dist[start.ff][start.ss][z] = {0, 0};
        q.insert({0, 0, start.ff, start.ss, z});
    }
    while (q.size())
    {
        int cdist = (*q.begin())[0];
        int ori = (*q.begin())[4];
        int locx = (*q.begin())[2];
        int locy = (*q.begin())[3];
        int extra = (*q.begin())[1];
        if (locx == target.ff && locy == target.ss)
            return cdist + ((extra + k - 1) / k);
        // assert(dist[loc.ff][loc.ss][ori] == cdist);

        // dbgm(cdist, locx, locy, ori);
        q.erase(q.begin());

        // if (dist[loc.ff][loc.ss][ori] < cdist)
        //     continue;
        for (int z = 0; z < 4; z++)
        {
            int nlocx = locx + dx[z];
            int nlocy = locy + dy[z];
            if (!check({nlocx, nlocy}) || maz[nlocx][nlocy])
                continue;
            // dbg("Here");
            int ndis = cdist;
            int nextra = extra;
            if (z != ori)
                ndis += nextra != 0, nextra = 0;
            nextra++;
            ndis += nextra / k;
            nextra %= k;
            if (ndis < dist[nlocx][nlocy][z].ff || (ndis == dist[nlocx][nlocy][z].ff && nextra < dist[nlocx][nlocy][z].ss))
            {
                dist[nlocx][nlocy][z] = {ndis, nextra};
                q.insert({ndis, nextra, nlocx, nlocy, z});
            }
        }
    }
    return -1;
}

int main()
{
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

    int temp, temp2;
    cin >> h >> w >> k >> temp >> temp2;
    temp--, temp2--;
    start = {temp, temp2};
    cin >> temp >> temp2;
    temp--, temp2--;
    target = {temp, temp2};
    maz.assign(h, vi(w));
    string stemp;
    for (int i = 0; i < h; i++)
    {
        cin >> stemp;
        assert(stemp.size() == w);
        for (int j = 0; j < w; j++)
        {
            maz[i][j] = stemp[j] != '.';
        }
    }

    cout << bfs();
}


Measured memory_bytes: 148752