#include <iostream>
#include <cmath>
#include <algorithm>
#include <stdio.h>
#include <cstring>
#include <string>
#include <cstdlib>
#include <vector>
#include <bitset>
#include <map>
#include <chrono>
#include <functional>
#include <unordered_set>
#include <unordered_map>
#include <numeric>
#include <queue>
#include <ctime>
#include <stack>
#include <set>
#include <list>
#include <deque>
#include <iomanip>
#include <sstream>
#include <fstream>
#include <stdarg.h>
#include <utility>

using namespace std;

#define pb push_back
#define mp make_pair
#define ll long long
#define ull unisgned long long
#define ld long double
#define all(a) a.begin(), a.end()
#define SORT(a) sort(all(a))
#define pii pair<int, int>
#define tii triple<int, int, int>
#define e 1e-7
#define PI acos(-1)
#define sz(a) (int)(a.size())
#define inf 1e17
#define vi vector<int>
#define F first
#define S second
#define rng(x) for(int _ = 0; _ < (x); _++)
#define rngi(i, x) for(int i = 0; i < (x); i++)
#define rngsi(s, i, x) for(int i = (s); i <(x); i++)
#define int long long
#define problem ""

template<typename A, typename B, typename C>
struct triple{
    A X;
    B Y;
    C Z;
    triple(A a = 0, B b = 0, C c = 0) :X(a), Y(b), Z(c) {}
};
template<typename A, typename B, typename C>
triple<A, B, C> make_triple(A a = 0, B b = 0, C c = 0){
    return triple<A, B, C>(a, b, c);
}
template<typename A, typename B, typename C>
bool operator<(const triple<A, B, C>& a, const triple<A, B, C>& b){
    if (a.X != b.X)
        return a.X < b.X;
    if (a.Y != b.Y)
        return a.Y < b.Y;
    return a.Z < b.Z;
}
template<typename T, typename SS>
ostream& operator<<(ostream& ofs, const pair<T, SS>& p){
    ofs << "( " << p.F << " , " << p.S << " )";
    return ofs;
}
template<typename T>
void print(T a){
    for (auto i : a)
        cout << i << ' ';
    cout << '\n';
}
template<typename T>
T max(T a, T b, T c){
    return max(a, max(b, c));
}
template<typename T>
T min(T a, T b, T c){
    return min(a, min(b, c));
}
template<typename T, typename D>
D min(T a){
    return *min_element(all(a));
}
template<typename T, typename D>
D max(T a){
    return *max_element(all(a));
}
struct custom_hash{
    static uint64_t splitmix64(uint64_t x){
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const{
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};
void solve(){
    int n, m, b;cin >> n >> m >> b;
    int x1, y1, x2, y2; cin >> x1 >> y1 >> x2 >> y2;
    vector<string> s(n); rngi(i, n) cin >> s[i];

    x1--;y1--;x2--;y2--;
    vector<pii> d{{-1, 0}, {+1, 0}, {0, -1}, {0, +1}};
    vi p(n * m * 4, inf);
    auto conv = [&](int i, int j, int k){
        return (i * m + j) * 4 + k;
    };
    auto vonc = [&](int z){
        return make_tuple(z/4/m, (z/4)%m,z%4);
    };
    set<pii> q;
    rngi(i, 4) q.insert(mp(0LL, conv(x1, y1, i)));
    for(auto v : q) p[v.second] = 0;
    while(sz(q)){
        int v =q.begin()->second;
        q.erase(q.begin());
        int i, j, k;
        tie(i,j,k) = vonc(v);
        rngi(t, 4){
            int ni = i + d[t].first;
            int nj = j + d[t].second;
            if(ni < 0 || nj < 0 || ni >= n || nj >= m || s[ni][nj] == '@') continue;
            int to = conv(ni,nj,t);
            int nv;
            if(t == k) nv = p[v] + 1;
            else nv = (p[v] + b - 1)/b*b + 1;
            if(nv < p[to]){
                q.erase(mp(p[to], to));
                p[to] = nv;
                q.insert(mp(p[to], to));
            }
        }
    }
    int ans = inf;
    rngi(i, 4)if(p[conv(x2,y2,i)] != inf) ans = min(ans, (p[conv(x2,y2,i)]+b-1)/b);
    cout << (ans == inf ? -1 : ans) << '\n';
};
signed main()
{
    if(0){
        freopen(problem".in", "r", stdin);
        freopen(problem".out", "w", stdout);
    }
    srand(time(NULL));
    cin.tie(0);
    cout.tie(0);
    ios_base::sync_with_stdio(false);
    int t = 1; //cin >> t;
    rng(t) solve();
}


Measured memory_bytes: 48804