#include <bits/stdc++.h>
using namespace std;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin);i<(end);i++)
#define REP(i, n) FOR(i,0,n)
#define IFOR(i, begin, end) for(int i=(end)-1;i>=(begin);i--)
#define IREP(i, n) IFOR(i,0,n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(),v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x) distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x) distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define Max(a, b) a = max(a, b)
#define Min(a, b) a = min(a, b)
#define bit(n) (1LL<<(n))
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v) { cout << #v << "=" << endl; REP(i_debug, v.size()){ cout << v[i_debug] << ","; } cout << endl; }
#define mdebug(m) { cout << #m << "=" << endl; REP(i_debug, m.size()){ REP(j_debug, m[i_debug].size()){ cout << m[i_debug][j_debug] << ","; } cout << endl;} }
#define Return(ans) { cout << (ans) << endl; return 0; }
#define pb push_back
#define fi first
#define se second
//#define int long long
//#define INF 1000000000000000000
template<typename T> istream &operator>>(istream &is, vector<T> &v){ for (auto &x : v) is >> x; return is; }
template<typename T> ostream &operator<<(ostream &os, vector<T> &v){ for(int i = 0; i < v.size(); i++) { cout << v[i]; if(i != v.size() - 1) cout << endl; }; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p){ cout << '(' << p.first << ',' << p.second << ')'; return os; }
template<typename T> void Out(T x) { cout << x << endl; }
template<typename T1, typename T2> void Ans(bool f, T1 y, T2 n) { if(f) Out(y); else Out(n); }

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using v_bool = vector<bool>;
using v_Pii = vector<Pii>;

//int dx[4] = {1,0,-1,0};
//int dy[4] = {0,1,0,-1};
//char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
//const int mod = 998244353;



signed main(){

    int H, W, K; cin >> H >> W >> K;
    int x1, y1, x2, y2; cin >> x1 >> y1 >> x2 >> y2;
    x1--; y1--; x2--; y2--;
    vector<string> c(H); cin >> c;

    vector<set<int>> sh(H), sw(W);
    mat vh(H), vw(W);
    REP(i, H){
        vh[i].pb(-1);
        REP(j, W){
            if(c[i][j] == '@') vh[i].pb(j);
            else sh[i].insert(j);
        }
        vh[i].pb(W);
    }
    REP(j, W){
        vw[j].pb(-1);
        REP(i, H){
            if(c[i][j] == '@') vw[j].pb(i);
            else sw[j].insert(i);
        }
        vw[j].pb(H);
    }

    queue<Pii> que;
    mat dp(H, vec(W, -1));
    dp[x1][y1] = 0;
    que.push(Pii(x1, y1));
    sh[x1].erase(y1); sw[y1].erase(x1);

    while(!que.empty()){
        Pii p = que.front(); que.pop();
        int x = p.fi, y = p.se;

        v_Pii erase_list;
        
        int j0 = Upper_bound(vh[x], y);
        int ymin = max(y - K, vh[x][j0 - 1] + 1), ymax = min(y + K, vh[x][j0] - 1);
        auto it = sh[x].lower_bound(ymin);
        while(it != sh[x].end() && *it <= ymax){
            int y0 = *it;
            dp[x][y0] = dp[x][y] + 1;
            erase_list.pb(Pii(x, y0));
            que.push(Pii(x, y0));
            it++;
        }

        int i0 = Upper_bound(vw[y], x);
        int xmin = max(x - K, vw[y][i0 - 1] + 1), xmax = min(x + K, vw[y][i0] - 1);
        it = sw[y].lower_bound(xmin);
        while(it != sw[y].end() && *it <= xmax){
            int x0 = *it;
            dp[x0][y] = dp[x][y] + 1;
            erase_list.pb(Pii(x0, y));
            que.push(Pii(x0, y));
            it++;
        }

        for(Pii q: erase_list){
            sh[q.fi].erase(q.se);
            sw[q.se].erase(q.fi);
        }

    }
    //mdebug(dp);
    Out(dp[x2][y2]);

    return 0;
}


Measured memory_bytes: 206900